diff --git a/benchmark/common/problems.h b/benchmark/common/problems.h
index c97c50eb03..7a7d41c169 100644
--- a/benchmark/common/problems.h
+++ b/benchmark/common/problems.h
@@ -4,7 +4,6 @@
 #pragma once
 
 #include "classes/box.h"
-#include "classes/coreData.h"
 #include "expression/variable.h"
 #include "main/dissolve.h"
 #include "nodes/configuration.h"
diff --git a/src/classes/CMakeLists.txt b/src/classes/CMakeLists.txt
index 10a5ad161f..2dcf789ffb 100644
--- a/src/classes/CMakeLists.txt
+++ b/src/classes/CMakeLists.txt
@@ -15,7 +15,6 @@ add_library(
   configuration_sites.cpp
   configuration_upkeep.cpp
   configurationAtom.cpp
-  coreData.cpp
   empiricalFormula.cpp
   fullPairIterator.cpp
   histogramSet.cpp
@@ -72,7 +71,6 @@ add_library(
   cellArray.h
   configuration.h
   configurationAtom.cpp
-  coreData.h
   empiricalFormula.h
   fragment.h
   histogramSet.h
diff --git a/src/classes/configuration_upkeep.cpp b/src/classes/configuration_upkeep.cpp
index d20f4332c6..c49fdbf33d 100644
--- a/src/classes/configuration_upkeep.cpp
+++ b/src/classes/configuration_upkeep.cpp
@@ -3,6 +3,7 @@
 
 #include "classes/box.h"
 #include "classes/cell.h"
+#include "classes/configuration.h"
 #include "classes/configurationAtom.h"
 #include "main/dissolve.h"
 
diff --git a/src/classes/coreData.cpp b/src/classes/coreData.cpp
deleted file mode 100644
index e6a239fe05..0000000000
--- a/src/classes/coreData.cpp
+++ /dev/null
@@ -1,130 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-// Copyright (c) 2026 Team Dissolve and contributors
-
-#include "classes/coreData.h"
-#include "base/sysFunc.h"
-#include "classes/atomType.h"
-#include "classes/configuration.h"
-#include "classes/species.h"
-#include "classes/speciesAngle.h"
-#include "classes/speciesBond.h"
-#include "classes/speciesTorsion.h"
-#include "main/dissolve.h"
-
-// Clear all data
-void CoreData::clear()
-{
-    configurations_.clear();
-    species_.clear();
-}
-
-/*
- * Species
- */
-
-// Add new Species
-Species *CoreData::addSpecies()
-{
-    auto &newSpecies = species_.emplace_back(std::make_unique<Species>());
-
-    // Create a suitable unique name
-    newSpecies->setName(
-        DissolveSys::uniqueName("NewSpecies", species_, [&](const auto &sp) { return newSpecies == sp ? "" : sp->name(); }));
-
-    return newSpecies.get();
-}
-
-// Remove specified Species
-void CoreData::removeSpecies(Species *sp)
-{
-    species_.erase(std::remove_if(species_.begin(), species_.end(), [&](const auto &p) { return sp == p.get(); }),
-                   species_.end());
-}
-
-// Return number of Species in list
-int CoreData::nSpecies() const { return species_.size(); }
-
-// Return core Species list
-std::vector<std::unique_ptr<Species>> &CoreData::species() { return species_; }
-
-const std::vector<std::unique_ptr<Species>> &CoreData::species() const { return species_; }
-
-// Search for Species by name
-Species *CoreData::findSpecies(std::string_view name) const
-{
-    auto it = std::find_if(species_.begin(), species_.end(),
-                           [name](const auto &sp) { return DissolveSys::sameString(sp->name(), name); });
-    if (it != species_.end())
-    {
-        return (*it).get();
-    }
-    else
-    {
-        return nullptr;
-    }
-}
-
-/*
- * Configuration
- */
-
-// Add new Configuration
-Configuration *CoreData::addConfiguration()
-{
-    auto &newConfiguration = configurations_.emplace_back(std::make_unique<Configuration>());
-
-    // Create a suitable unique name
-    newConfiguration->setName(DissolveSys::uniqueName("NewConfiguration", configurations_, [&](const auto &cfg)
-                                                      { return newConfiguration == cfg ? "" : cfg->name(); }));
-
-    return newConfiguration.get();
-}
-
-// Remove specified Configuration
-void CoreData::removeConfiguration(Configuration *cfg)
-{
-    configurations_.erase(
-        std::remove_if(configurations_.begin(), configurations_.end(), [cfg](const auto &c) { return cfg == c.get(); }),
-        configurations_.end());
-}
-
-// Return number of Configurations in list
-int CoreData::nConfigurations() const { return configurations_.size(); }
-
-// Return core Configurations list
-std::vector<std::unique_ptr<Configuration>> &CoreData::configurations() { return configurations_; }
-
-const std::vector<std::unique_ptr<Configuration>> &CoreData::configurations() const { return configurations_; }
-
-// Return nth Configuration in list
-Configuration *CoreData::configuration(int n) { return configurations_[n].get(); }
-
-// Search for Configuration by name
-Configuration *CoreData::findConfiguration(std::string_view name) const
-{
-    auto it = std::find_if(configurations_.begin(), configurations_.end(),
-                           [&name](const auto &cfg) { return DissolveSys::sameString(cfg->name(), name); });
-    if (it == configurations_.end())
-        return nullptr;
-    return it->get();
-}
-
-// Find configuration by 'nice' name
-Configuration *CoreData::findConfigurationByNiceName(std::string_view name) const
-{
-    auto it = std::find_if(configurations().begin(), configurations().end(),
-                           [&name](const auto &cfg) { return DissolveSys::sameString(name, cfg->name()); });
-    if (it == configurations().end())
-        return nullptr;
-    return it->get();
-}
-
-/*
- * Input Filename
- */
-
-// Set pointer to the current input filename
-void CoreData::setInputFilename(std::string_view filename) { inputFilename_ = filename; }
-
-// Return the current input filename
-std::string_view CoreData::inputFilename() const { return inputFilename_; }
diff --git a/src/classes/coreData.h b/src/classes/coreData.h
deleted file mode 100644
index 16896cc40f..0000000000
--- a/src/classes/coreData.h
+++ /dev/null
@@ -1,87 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-// Copyright (c) 2026 Team Dissolve and contributors
-
-#pragma once
-
-#include "base/version.h"
-#include "classes/configuration.h"
-#include "classes/pairPotentialOverride.h"
-#include "classes/species.h"
-#include "data/elements.h"
-#include "templates/optionalRef.h"
-#include <list>
-#include <memory>
-#include <optional>
-#include <vector>
-
-// Forward Declarations
-class Dissolve;
-class Module;
-class ModuleLayer;
-
-// Core Data Container
-class CoreData
-{
-    public:
-    CoreData() = default;
-    ~CoreData() = default;
-    // Clear all data
-    void clear();
-
-    /*
-     * Species
-     */
-    private:
-    // Core Species list
-    std::vector<std::unique_ptr<Species>> species_;
-
-    public:
-    // Add new Species
-    Species *addSpecies();
-    // Remove specified Species
-    void removeSpecies(Species *sp);
-    // Return number of Species in list
-    int nSpecies() const;
-    // Return core Species list
-    std::vector<std::unique_ptr<Species>> &species();
-    const std::vector<std::unique_ptr<Species>> &species() const;
-    // Search for Species by name
-    Species *findSpecies(std::string_view name) const;
-
-    /*
-     * Configurations
-     */
-    private:
-    // Core Configurations list
-    std::vector<std::unique_ptr<Configuration>> configurations_;
-
-    public:
-    // Add new Configuration
-    Configuration *addConfiguration();
-    // Remove specified Configuration
-    void removeConfiguration(Configuration *cfg);
-    // Return number of Configuration in list
-    int nConfigurations() const;
-    // Return core Configuration list
-    std::vector<std::unique_ptr<Configuration>> &configurations();
-    const std::vector<std::unique_ptr<Configuration>> &configurations() const;
-    // Return nth Configuration in list
-    Configuration *configuration(int n);
-    // Search for Configuration by name
-    Configuration *findConfiguration(std::string_view name) const;
-    // Find configuration by 'nice' name
-    Configuration *findConfigurationByNiceName(std::string_view name) const;
-
-    /*
-     * Input Filename
-     */
-    private:
-    // Current input filename (mirroring that in Dissolve)
-    std::string inputFilename_;
-
-    public:
-    // Set current input filename
-    void setInputFilename(std::string_view filename);
-    // Return the current input filename
-    std::string_view inputFilename() const;
-};
diff --git a/src/classes/isotopologue.cpp b/src/classes/isotopologue.cpp
index 59214fe5e2..f3eb152ff4 100644
--- a/src/classes/isotopologue.cpp
+++ b/src/classes/isotopologue.cpp
@@ -3,7 +3,6 @@
 
 #include "classes/isotopologue.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "data/isotopes.h"
 
diff --git a/src/classes/isotopologueSet.cpp b/src/classes/isotopologueSet.cpp
index 89e20ed7b8..aab8e6c04e 100644
--- a/src/classes/isotopologueSet.cpp
+++ b/src/classes/isotopologueSet.cpp
@@ -3,7 +3,6 @@
 
 #include "classes/isotopologueSet.h"
 #include "base/lineParser.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include <algorithm>
 
diff --git a/src/classes/isotopologueSet.h b/src/classes/isotopologueSet.h
index 8f29de028f..f79cb4db58 100644
--- a/src/classes/isotopologueSet.h
+++ b/src/classes/isotopologueSet.h
@@ -4,7 +4,6 @@
 #pragma once
 
 #include "base/serialiser.h"
-#include "classes/coreData.h"
 
 // Forward Declarations
 class Species;
diff --git a/src/classes/speciesAngle.cpp b/src/classes/speciesAngle.cpp
index ce2658f45e..1f8350ed11 100644
--- a/src/classes/speciesAngle.cpp
+++ b/src/classes/speciesAngle.cpp
@@ -2,10 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "classes/speciesAngle.h"
-#include "classes/coreData.h"
+#include "classes/species.h"
 #include "classes/speciesAtom.h"
 #include "math/mathFunc.h"
-#include <map>
 
 SpeciesAngle::SpeciesAngle() : SpeciesIntra(nullptr, AngleFunctions::Form::None) {}
 
diff --git a/src/classes/speciesAtom.cpp b/src/classes/speciesAtom.cpp
index 7b0d3a2787..516b1341ac 100644
--- a/src/classes/speciesAtom.cpp
+++ b/src/classes/speciesAtom.cpp
@@ -4,7 +4,6 @@
 #include "classes/speciesAtom.h"
 #include "classes/atomType.h"
 #include "classes/box.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "classes/speciesBond.h"
 #include <algorithm>
diff --git a/src/classes/speciesBond.cpp b/src/classes/speciesBond.cpp
index be8fd8d3af..94aae5fe58 100644
--- a/src/classes/speciesBond.cpp
+++ b/src/classes/speciesBond.cpp
@@ -2,11 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "classes/speciesBond.h"
-#include "base/sysFunc.h"
-#include "classes/coreData.h"
+#include "classes/species.h"
 #include "classes/speciesAtom.h"
 #include "data/atomicMasses.h"
-#include <map>
 
 SpeciesBond::SpeciesBond() : SpeciesIntra(nullptr, BondFunctions::Form::None) {}
 
diff --git a/src/classes/speciesImproper.cpp b/src/classes/speciesImproper.cpp
index 9a62b708f0..181b898f75 100644
--- a/src/classes/speciesImproper.cpp
+++ b/src/classes/speciesImproper.cpp
@@ -2,7 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "classes/speciesImproper.h"
-#include "classes/coreData.h"
+#include "classes/species.h"
 #include "classes/speciesAtom.h"
 #include "classes/speciesTorsion.h"
 
diff --git a/src/classes/speciesSite.cpp b/src/classes/speciesSite.cpp
index 262d1590bd..11fe56feb3 100644
--- a/src/classes/speciesSite.cpp
+++ b/src/classes/speciesSite.cpp
@@ -3,7 +3,6 @@
 
 #include "classes/speciesSite.h"
 #include "base/lineParser.h"
-#include "classes/coreData.h"
 #include "classes/site.h"
 #include "classes/species.h"
 #include "data/atomicMasses.h"
diff --git a/src/classes/speciesTorsion.cpp b/src/classes/speciesTorsion.cpp
index cd75417d5d..ff35c37cb8 100644
--- a/src/classes/speciesTorsion.cpp
+++ b/src/classes/speciesTorsion.cpp
@@ -2,10 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "classes/speciesTorsion.h"
-#include "classes/coreData.h"
+#include "classes/species.h"
 #include "classes/speciesAtom.h"
 #include "math/mathFunc.h"
-#include <map>
 
 SpeciesTorsion::SpeciesTorsion() : SpeciesIntra(nullptr, TorsionFunctions::Form::None) {}
 
diff --git a/src/classes/species_intra.cpp b/src/classes/species_intra.cpp
index 525171ac21..629684ee0d 100644
--- a/src/classes/species_intra.cpp
+++ b/src/classes/species_intra.cpp
@@ -4,7 +4,6 @@
 #include "base/sysFunc.h"
 #include "classes/atomType.h"
 #include "classes/box.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "templates/algorithms.h"
 #include <algorithm>
diff --git a/src/classes/torsionFunctions.cpp b/src/classes/torsionFunctions.cpp
index 0bbb3eb253..ca9d920518 100644
--- a/src/classes/torsionFunctions.cpp
+++ b/src/classes/torsionFunctions.cpp
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Copyright (c) 2026 Team Dissolve and contributors
 
-#include "classes/coreData.h"
 #include "classes/speciesAtom.h"
 #include "classes/speciesTorsion.h"
 #include <map>
diff --git a/src/data/ff/camelloneBKS/camelloneBKS.cpp b/src/data/ff/camelloneBKS/camelloneBKS.cpp
index 7c0d466406..fb7f535594 100644
--- a/src/data/ff/camelloneBKS/camelloneBKS.cpp
+++ b/src/data/ff/camelloneBKS/camelloneBKS.cpp
@@ -4,7 +4,6 @@
 #include "data/ff/camelloneBKS/camelloneBKS.h"
 #include "base/sysFunc.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 #include "classes/speciesAtom.h"
 #include "data/ff/angleTerm.h"
 #include "data/ff/atomType.h"
diff --git a/src/data/ff/ff.cpp b/src/data/ff/ff.cpp
index 742d3062f4..3bb17c4ad0 100644
--- a/src/data/ff/ff.cpp
+++ b/src/data/ff/ff.cpp
@@ -4,7 +4,6 @@
 #include "data/ff/ff.h"
 #include "classes/atomType.h"
 #include "classes/box.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "classes/speciesAtom.h"
 #include "classes/speciesBond.h"
diff --git a/src/data/ff/uff/uff.cpp b/src/data/ff/uff/uff.cpp
index dcdea98a99..b584480ecd 100644
--- a/src/data/ff/uff/uff.cpp
+++ b/src/data/ff/uff/uff.cpp
@@ -3,7 +3,6 @@
 
 #include "data/ff/uff/uff.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "data/elements.h"
 #include "math/mathFunc.h"
diff --git a/src/data/ff/uff/uff4MOF.cpp b/src/data/ff/uff/uff4MOF.cpp
index e25c748f1b..1bf17be3d7 100644
--- a/src/data/ff/uff/uff4MOF.cpp
+++ b/src/data/ff/uff/uff4MOF.cpp
@@ -3,7 +3,6 @@
 
 #include "data/ff/uff/uff4MOF.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 #include "data/elements.h"
 
diff --git a/src/dissolve-gui-qml.cpp b/src/dissolve-gui-qml.cpp
index 063fd5aabb..5682774b85 100644
--- a/src/dissolve-gui-qml.cpp
+++ b/src/dissolve-gui-qml.cpp
@@ -17,8 +17,7 @@
 int main(int args, char **argv)
 {
     // Instantiate main classes
-    CoreData coreData;
-    Dissolve dissolve(coreData);
+    Dissolve dissolve;
 
     DissolveModel dissolveModel;
     dissolveModel.setDissolve(dissolve);
diff --git a/src/gui/configurationViewerWidget.cpp b/src/gui/configurationViewerWidget.cpp
index efd3209c53..591857312f 100644
--- a/src/gui/configurationViewerWidget.cpp
+++ b/src/gui/configurationViewerWidget.cpp
@@ -3,7 +3,6 @@
 
 #include "gui/configurationViewerWidget.h"
 #include "classes/configuration.h"
-#include "classes/coreData.h"
 #include "classes/empiricalFormula.h"
 #include "gui/widgets/elementSelector.h"
 #include "main/dissolve.h"
diff --git a/src/gui/getConfigurationNameDialog.cpp b/src/gui/getConfigurationNameDialog.cpp
index 0fa9c7ae47..5df7bb16e5 100644
--- a/src/gui/getConfigurationNameDialog.cpp
+++ b/src/gui/getConfigurationNameDialog.cpp
@@ -4,7 +4,6 @@
 #include "gui/getConfigurationNameDialog.h"
 #include "base/sysFunc.h"
 #include "classes/configuration.h"
-#include "classes/coreData.h"
 
 GetConfigurationNameDialog::GetConfigurationNameDialog(QWidget *parent, const CoreData &coreData) : coreData_(coreData)
 {
diff --git a/src/gui/getModuleLayerNameDialog.cpp b/src/gui/getModuleLayerNameDialog.cpp
index 33489dfd4e..4e646d9136 100644
--- a/src/gui/getModuleLayerNameDialog.cpp
+++ b/src/gui/getModuleLayerNameDialog.cpp
@@ -3,7 +3,6 @@
 
 #include "gui/getModuleLayerNameDialog.h"
 #include "base/sysFunc.h"
-#include "classes/coreData.h"
 #include "module/layer.h"
 
 GetModuleLayerNameDialog::GetModuleLayerNameDialog(QWidget *parent, const std::vector<std::unique_ptr<ModuleLayer>> &layers)
diff --git a/src/gui/getSpeciesNameDialog.cpp b/src/gui/getSpeciesNameDialog.cpp
index ace6d31ca7..5a86d145be 100644
--- a/src/gui/getSpeciesNameDialog.cpp
+++ b/src/gui/getSpeciesNameDialog.cpp
@@ -3,7 +3,6 @@
 
 #include "gui/getSpeciesNameDialog.h"
 #include "base/sysFunc.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 
 GetSpeciesNameDialog::GetSpeciesNameDialog(QWidget *parent, const CoreData &coreData) : coreData_(coreData)
diff --git a/src/gui/models/addSpeciesInfoModel.cpp b/src/gui/models/addSpeciesInfoModel.cpp
index 770d4c851d..0f557365bf 100644
--- a/src/gui/models/addSpeciesInfoModel.cpp
+++ b/src/gui/models/addSpeciesInfoModel.cpp
@@ -4,7 +4,7 @@
 #include "gui/models/addSpeciesInfoModel.h"
 #include "base/sysFunc.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
+#include "classes/species.h"
 
 /*
  * AddSpeciesInfo
diff --git a/src/gui/models/atomTypeModel.cpp b/src/gui/models/atomTypeModel.cpp
index 28cbec7089..0732d1f211 100644
--- a/src/gui/models/atomTypeModel.cpp
+++ b/src/gui/models/atomTypeModel.cpp
@@ -4,7 +4,6 @@
 #include "gui/models/atomTypeModel.h"
 #include "base/sysFunc.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 #include "templates/algorithms.h"
 
 void AtomTypeModel::reset()
diff --git a/src/gui/models/commonAngleModel.cpp b/src/gui/models/commonAngleModel.cpp
index 1ea7366799..6e98e6e4e8 100644
--- a/src/gui/models/commonAngleModel.cpp
+++ b/src/gui/models/commonAngleModel.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonAngleModel.h"
+#include "classes/species.h"
 
 CommonAngleModel::CommonAngleModel(Species *species) : CommonTermModel(species), sourceData_(species->commonAngles())
 {
diff --git a/src/gui/models/commonBondModel.cpp b/src/gui/models/commonBondModel.cpp
index b5621987d2..0962c75af2 100644
--- a/src/gui/models/commonBondModel.cpp
+++ b/src/gui/models/commonBondModel.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonBondModel.h"
+#include "classes/species.h"
 
 CommonBondModel::CommonBondModel(Species *species) : CommonTermModel(species), sourceData_(species->commonBonds())
 {
diff --git a/src/gui/models/commonImproperModel.cpp b/src/gui/models/commonImproperModel.cpp
index 72e86ad847..a585cf6a45 100644
--- a/src/gui/models/commonImproperModel.cpp
+++ b/src/gui/models/commonImproperModel.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonImproperModel.h"
+#include "classes/species.h"
 
 CommonImproperModel::CommonImproperModel(Species *species) : CommonTermModel(species), sourceData_(species->commonImpropers())
 {
diff --git a/src/gui/models/commonTermModel.cpp b/src/gui/models/commonTermModel.cpp
index e044633460..cfee51f31c 100644
--- a/src/gui/models/commonTermModel.cpp
+++ b/src/gui/models/commonTermModel.cpp
@@ -2,6 +2,8 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonTermModel.h"
+#include "classes/speciesAtom.h"
+#include "classes/speciesBond.h"
 
 CommonTermModel::CommonTermModel(Species *species) : species_(species) {}
 
diff --git a/src/gui/models/commonTermModel.h b/src/gui/models/commonTermModel.h
index 434883573e..a182c6f1a2 100644
--- a/src/gui/models/commonTermModel.h
+++ b/src/gui/models/commonTermModel.h
@@ -3,12 +3,14 @@
 
 #pragma once
 
-#include "classes/coreData.h"
 #include <QAbstractTableModel>
 #include <QIcon>
 #include <QModelIndex>
 #include <QObject>
 
+// Forward Declarations
+class Species;
+
 namespace CommonTermModelData
 {
 // Enumerated data items for terms
diff --git a/src/gui/models/commonTermTreeModel.cpp b/src/gui/models/commonTermTreeModel.cpp
index 9a394aabba..9431f32670 100644
--- a/src/gui/models/commonTermTreeModel.cpp
+++ b/src/gui/models/commonTermTreeModel.cpp
@@ -2,6 +2,8 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonTermTreeModel.h"
+#include "classes/speciesAtom.h"
+#include "classes/speciesBond.h"
 
 MasterTermTreeModel::MasterTermTreeModel(Species *species)
     : bondModel_(species), angleModel_(species), torsionModel_(species), improperModel_(species)
diff --git a/src/gui/models/commonTorsionModel.cpp b/src/gui/models/commonTorsionModel.cpp
index 7a2f293a90..ed22aa1015 100644
--- a/src/gui/models/commonTorsionModel.cpp
+++ b/src/gui/models/commonTorsionModel.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/commonTorsionModel.h"
+#include "classes/species.h"
 
 CommonTorsionModel::CommonTorsionModel(Species *species) : CommonTermModel(species), sourceData_(species->commonTorsions())
 {
diff --git a/src/gui/models/dissolveModel.cpp b/src/gui/models/dissolveModel.cpp
index 6bb436a7ed..4e42f05450 100644
--- a/src/gui/models/dissolveModel.cpp
+++ b/src/gui/models/dissolveModel.cpp
@@ -22,7 +22,6 @@ void DissolveModel::setDissolve(Dissolve &dissolve)
     dissolve_ = &dissolve;
 
     // commons_ = std::make_unique<MasterTermTreeModel>(dissolve_->coreData());
-    configurationModel_.setData(dissolve_->coreData().configurations());
     Q_EMIT modelsUpdated();
 }
 
@@ -36,7 +35,6 @@ void DissolveModel::update()
         commons_->torsionModel_.reset();
         commons_->improperModel_.reset();
     }
-    configurationModel_.reset();
     Q_EMIT modelsUpdated();
 }
 
@@ -104,16 +102,12 @@ int DissolveModel::nCommonImpropers()
     return commons_->improperModel_.rowCount();
 }
 
-// The Configuration Model
-ConfigurationModel *DissolveModel::configurationsModel() { return &configurationModel_; }
-
 // Getter for filename
 QUrl DissolveModel::fileName() { return QUrl(dissolve_->inputFilename().data()); }
 
 void DissolveModel::loadInput(QUrl filename)
 {
     dissolve_->loadInput(filename.toLocalFile().toStdString());
-    configurationModel_.reset();
     Q_EMIT(modelsUpdated());
 }
 
diff --git a/src/gui/models/dissolveModel.h b/src/gui/models/dissolveModel.h
index ab4ca6accd..cecf996be1 100644
--- a/src/gui/models/dissolveModel.h
+++ b/src/gui/models/dissolveModel.h
@@ -23,8 +23,6 @@ class DissolveModel : public QObject
     Q_PROPERTY(const CommonTorsionModel *commonTorsionsModel READ commonTorsionsModel NOTIFY commonsChanged)
     // The Master Improper Model
     Q_PROPERTY(const CommonImproperModel *commonImpropersModel READ commonImpropersModel NOTIFY commonsChanged)
-    // The Configuration Model
-    Q_PROPERTY(const ConfigurationModel *configurationsModel READ configurationsModel NOTIFY configurationsChanged)
     // File to load
     Q_PROPERTY(QUrl file READ fileName WRITE loadInput NOTIFY modelsUpdated)
     // The main graph
@@ -33,7 +31,6 @@ class DissolveModel : public QObject
     private:
     // Master terms model
     std::unique_ptr<MasterTermTreeModel> commons_ = nullptr;
-    ConfigurationModel configurationModel_;
 
     public:
     // Getter for filename
@@ -51,8 +48,6 @@ class DissolveModel : public QObject
 
     // Species model has been replaced
     void speciesChanged();
-    // Configurations model has been replaced
-    void configurationsChanged();
     // ModuleLayers model has been replaced
     void moduleLayersChanged();
 
@@ -80,8 +75,6 @@ class DissolveModel : public QObject
     const CommonImproperModel *commonImpropersModel() const;
     // The number of common impropers
     int nCommonImpropers();
-    // The Configurations Model
-    ConfigurationModel *configurationsModel();
 
     /*
      * Data
diff --git a/src/gui/models/isotopologueSetModel.h b/src/gui/models/isotopologueSetModel.h
index eb6a1cae94..b4306e666e 100644
--- a/src/gui/models/isotopologueSetModel.h
+++ b/src/gui/models/isotopologueSetModel.h
@@ -4,6 +4,7 @@
 #pragma once
 
 #include "classes/isotopologueSet.h"
+#include "templates/optionalRef.h"
 #include <QAbstractItemModel>
 #include <QModelIndex>
 
diff --git a/src/gui/models/speciesImproperModel.cpp b/src/gui/models/speciesImproperModel.cpp
index 5ca6aad867..1adb18752b 100644
--- a/src/gui/models/speciesImproperModel.cpp
+++ b/src/gui/models/speciesImproperModel.cpp
@@ -2,7 +2,8 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/speciesImproperModel.h"
-#include "classes/coreData.h"
+#include "classes/speciesAtom.h"
+#include "classes/speciesBond.h"
 
 SpeciesImproperModel::SpeciesImproperModel() : impropers_(nullptr) {}
 
diff --git a/src/gui/models/speciesTorsionModel.cpp b/src/gui/models/speciesTorsionModel.cpp
index ff44594443..d3c47c1e82 100644
--- a/src/gui/models/speciesTorsionModel.cpp
+++ b/src/gui/models/speciesTorsionModel.cpp
@@ -2,7 +2,8 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/models/speciesTorsionModel.h"
-#include "classes/coreData.h"
+#include "classes/speciesAtom.h"
+#include "classes/speciesBond.h"
 
 SpeciesTorsionModel::SpeciesTorsionModel() : torsions_(nullptr) {}
 
diff --git a/src/gui/models/xmlAtomModel.cpp b/src/gui/models/xmlAtomModel.cpp
index f86c7983c8..c05f5b00e0 100644
--- a/src/gui/models/xmlAtomModel.cpp
+++ b/src/gui/models/xmlAtomModel.cpp
@@ -7,8 +7,6 @@
 #include <QColor>
 #include <pugixml.hpp>
 
-XmlAtomModel::XmlAtomModel(const CoreData &coreData) : coreData_(coreData) {}
-
 void XmlAtomModel::readFile(const pugi::xml_node &root)
 {
     beginResetModel();
diff --git a/src/gui/models/xmlAtomModel.h b/src/gui/models/xmlAtomModel.h
index 42d6d1742c..c52a236e01 100644
--- a/src/gui/models/xmlAtomModel.h
+++ b/src/gui/models/xmlAtomModel.h
@@ -22,15 +22,12 @@ class XmlAtomModel : public QAbstractTableModel
 
     private:
     std::vector<XmlAtomData> atoms_;
-    const CoreData &coreData_;
 
     public Q_SLOTS:
     // Read from an XML file
     void readFile(const pugi::xml_node &);
 
     public:
-    XmlAtomModel(const CoreData &coreData);
-
     int rowCount(const QModelIndex &parent = QModelIndex()) const override;
 
     int columnCount(const QModelIndex &parent = QModelIndex()) const override;
diff --git a/src/gui/models/xmlTreeModel.cpp b/src/gui/models/xmlTreeModel.cpp
index 8857aed3a3..c1b4f35af6 100644
--- a/src/gui/models/xmlTreeModel.cpp
+++ b/src/gui/models/xmlTreeModel.cpp
@@ -7,8 +7,6 @@
 
 XmlTreeIndex::XmlTreeIndex(int row, int column, pugi::xml_node node) : row_(row), column_(column), node_(node) {}
 
-XmlTreeModel::XmlTreeModel(const CoreData &coreData) : QAbstractItemModel(), atoms_(coreData) {}
-
 void XmlTreeModel::readFile(const pugi::xml_node &root)
 {
     beginResetModel();
diff --git a/src/gui/models/xmlTreeModel.h b/src/gui/models/xmlTreeModel.h
index cc490447c1..ce67bb0d42 100644
--- a/src/gui/models/xmlTreeModel.h
+++ b/src/gui/models/xmlTreeModel.h
@@ -49,8 +49,6 @@ class XmlTreeModel : public QAbstractItemModel
     void readFile(const pugi::xml_node &);
 
     public:
-    XmlTreeModel(const CoreData &coreData);
-
     QModelIndex parent(const QModelIndex &index) const override;
 
     QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const override;
diff --git a/src/gui/selectAtomTypeDialog.cpp b/src/gui/selectAtomTypeDialog.cpp
index 7d0797e81c..b49f01c1ec 100644
--- a/src/gui/selectAtomTypeDialog.cpp
+++ b/src/gui/selectAtomTypeDialog.cpp
@@ -2,7 +2,6 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/selectAtomTypeDialog.h"
-#include "classes/coreData.h"
 #include "gui/selectAtomTypeWidget.h"
 
 SelectAtomTypeDialog::SelectAtomTypeDialog(QWidget *parent, const CoreData &coreData, QString dialogTitle)
diff --git a/src/gui/selectAtomTypeWidget.cpp b/src/gui/selectAtomTypeWidget.cpp
index e4bf620b80..84a65a452a 100644
--- a/src/gui/selectAtomTypeWidget.cpp
+++ b/src/gui/selectAtomTypeWidget.cpp
@@ -3,7 +3,6 @@
 
 #include "gui/selectAtomTypeWidget.h"
 #include "classes/atomType.h"
-#include "classes/coreData.h"
 
 SelectAtomTypeWidget::SelectAtomTypeWidget(QWidget *parent) : QWidget(parent)
 {
diff --git a/src/gui/selectSpeciesDialog.cpp b/src/gui/selectSpeciesDialog.cpp
index 97695ca6b8..fd95fed718 100644
--- a/src/gui/selectSpeciesDialog.cpp
+++ b/src/gui/selectSpeciesDialog.cpp
@@ -2,7 +2,6 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/selectSpeciesDialog.h"
-#include "classes/coreData.h"
 #include "data/ff/ff.h"
 #include "gui/selectSpeciesWidget.h"
 
diff --git a/src/gui/selectSpeciesWidget.cpp b/src/gui/selectSpeciesWidget.cpp
index 0a4b614cc7..f42acd1a12 100644
--- a/src/gui/selectSpeciesWidget.cpp
+++ b/src/gui/selectSpeciesWidget.cpp
@@ -2,7 +2,6 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "gui/selectSpeciesWidget.h"
-#include "classes/coreData.h"
 #include "classes/species.h"
 
 SelectSpeciesWidget::SelectSpeciesWidget(QWidget *parent) : QWidget(parent)
diff --git a/src/main/dissolve.cpp b/src/main/dissolve.cpp
index adb594d74c..dc663719fe 100644
--- a/src/main/dissolve.cpp
+++ b/src/main/dissolve.cpp
@@ -5,7 +5,7 @@
 #include "classes/kVector.h"
 #include "nodes/dissolve.h"
 
-Dissolve::Dissolve(CoreData &coreData) : coreData_(coreData)
+Dissolve::Dissolve()
 {
     // Set core simulation variables
     restartFileFrequency_ = 10;
@@ -24,18 +24,9 @@ Dissolve::~Dissolve() { clear(); }
 
 DissolveGraph *Dissolve::graph() { return graphNode_.get(); }
 
-// Return reference to CoreData
-CoreData &Dissolve::coreData() { return coreData_; }
-
-const CoreData &Dissolve::coreData() const { return coreData_; }
-
 // Clear all data
 void Dissolve::clear()
 {
-    // Core
-    Messenger::printVerbose("Clearing Core Data...\n");
-    coreData_.clear();
-
     // PairPotentials
     Messenger::printVerbose("Clearing Pair Potentials...\n");
     useCombinationRules_ = true;
diff --git a/src/main/dissolve.h b/src/main/dissolve.h
index bdcd6e3399..19285823f0 100644
--- a/src/main/dissolve.h
+++ b/src/main/dissolve.h
@@ -5,8 +5,6 @@
 
 #include "base/serialiser.h"
 #include "base/timer.h"
-#include "classes/configuration.h"
-#include "classes/coreData.h"
 #include "classes/pairPotential.h"
 #include "classes/potentialMap.h"
 #include "math/sampledDouble.h"
@@ -23,20 +21,10 @@ class Molecule;
 class Dissolve : public Serialisable
 {
     public:
-    Dissolve(CoreData &coreData);
+    Dissolve();
     ~Dissolve();
 
-    /*
-     * Core
-     */
-    private:
-    // Reference to CoreData
-    CoreData &coreData_;
-
     public:
-    // Return reference to CoreData
-    CoreData &coreData();
-    const CoreData &coreData() const;
     // Clear all data
     void clear();
     // TOML Toggle
diff --git a/src/main/io.cpp b/src/main/io.cpp
index 71372c5a70..264a561358 100644
--- a/src/main/io.cpp
+++ b/src/main/io.cpp
@@ -49,13 +49,9 @@ void Dissolve::serialise(std::string tag, SerialisedValue &target) const
 
     root["version"] = Version::semantic();
 
-    Serialisable::fromVectorToTable<>(coreData_.species(), "species", root);
-
     root["pairPotentials"] = serialisePairPotentials();
 
     graphNode_->serialise("graph", root);
-
-    Serialisable::fromVectorToTable(coreData_.configurations(), "configurations", root);
 }
 
 // Read pair potentials from a serialisable value
@@ -100,17 +96,6 @@ void Dissolve::deserialise(const SerialisedValue &originalNode)
     Serialisable::optionalOn(node, "graph", [this](const auto node) { graphNode_->deserialise(node); });
 
     Serialisable::optionalOn(node, "pairPotentials", [this](const auto node) { deserialisePairPotentials(node); });
-
-    toMap(node, "species", [this](const std::string &name, const SerialisedValue &data)
-          { coreData_.species().emplace_back(std::make_unique<Species>(name))->deserialise(data); });
-
-    toMap(node, "configurations",
-          [this](const std::string &name, const SerialisedValue &data)
-          {
-              auto *cfg = coreData_.addConfiguration();
-              cfg->setName(name);
-              cfg->deserialise(data);
-          });
 }
 
 // Load input from supplied file
@@ -184,7 +169,6 @@ bool Dissolve::hasInputFilename() const { return (!inputFilename_.empty()); }
 void Dissolve::setInputFilename(std::string_view filename)
 {
     inputFilename_ = filename;
-    coreData_.setInputFilename(filename);
 
     restartFilename_ = std::format("{}.restart", inputFilename_);
 }
diff --git a/src/main/simulation.cpp b/src/main/simulation.cpp
index 6d8c89485e..34cb4e750b 100644
--- a/src/main/simulation.cpp
+++ b/src/main/simulation.cpp
@@ -19,11 +19,12 @@ bool Dissolve::prepare()
     Messenger::banner("Preparing Simulation");
 
     // Check Species
-    for (const auto &sp : coreData_.species())
-    {
-        if (!sp->checkSetUp())
-            return false;
-    }
+    // TODO DISSOLVE2
+    // for (const auto &sp : coreData_.species())
+    // {
+    //     if (!sp->checkSetUp())
+    //         return false;
+    // }
 
     // Store / update last-used pair potential cutoff
     // If lastPairPotentialCutoff is nullopt, store the current value and move on leaving the cutoff to use as nullopt.
@@ -42,25 +43,27 @@ bool Dissolve::prepare()
         return false;
 
     // Check Configurations
-    std::set<const Species *> globalUsedSpecies;
-    for (auto &cfg : coreData_.configurations())
-    {
-        if (newPairPotentialRange)
-            cfg->updateCells();
-
-        // Check Box extent against pair potential range
-        auto maxPPRange = cfg->box().inscribedSphereRadius();
-        if (PairPotential::range() > maxPPRange)
-            return Messenger::error("PairPotential range ({}) is longer than the shortest non-minimum image distance ({}).\n",
-                                    PairPotential::range(), maxPPRange);
-
-        // Update species usage for the next check
-        for (auto &[sp, pop] : cfg->speciesPopulations())
-            globalUsedSpecies.emplace(sp);
-    }
-
-    // If we have no configurations, check all species regardless
-    if (coreData_.nConfigurations() == 0)
-        for (const auto &sp : coreData_.species())
-            globalUsedSpecies.emplace(sp.get());
+    // TODO DISSOLVE2
+    // std::set<const Species *> globalUsedSpecies;
+    // for (auto &cfg : coreData_.configurations())
+    // {
+    //     if (newPairPotentialRange)
+    //         cfg->updateCells();
+    //
+    //     // Check Box extent against pair potential range
+    //     auto maxPPRange = cfg->box().inscribedSphereRadius();
+    //     if (PairPotential::range() > maxPPRange)
+    //         return Messenger::error("PairPotential range ({}) is longer than the shortest non-minimum image distance
+    //         ({}).\n",
+    //                                 PairPotential::range(), maxPPRange);
+    //
+    //     // Update species usage for the next check
+    //     for (auto &[sp, pop] : cfg->speciesPopulations())
+    //         globalUsedSpecies.emplace(sp);
+    // }
+    //
+    // // If we have no configurations, check all species regardless
+    // if (coreData_.nConfigurations() == 0)
+    //     for (const auto &sp : coreData_.species())
+    //         globalUsedSpecies.emplace(sp.get());
 }
diff --git a/src/nodes/angle.h b/src/nodes/angle.h
index c4a9b7a453..3e2bef9d95 100644
--- a/src/nodes/angle.h
+++ b/src/nodes/angle.h
@@ -10,6 +10,9 @@
 #include "math/rangedVector3.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class AngleNode : public Node
 {
     public:
diff --git a/src/nodes/averageMolecule.cpp b/src/nodes/averageMolecule.cpp
index 45f61d22b9..497d570e68 100644
--- a/src/nodes/averageMolecule.cpp
+++ b/src/nodes/averageMolecule.cpp
@@ -2,6 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/averageMolecule.h"
+#include "classes/configuration.h"
+#include "classes/species.h"
+#include "classes/speciesSite.h"
 
 AverageMoleculeNode::AverageMoleculeNode(Graph *parentGraph) : Node(parentGraph)
 {
diff --git a/src/nodes/averageMolecule.h b/src/nodes/averageMolecule.h
index cff4f67afd..d45c8bd9b4 100644
--- a/src/nodes/averageMolecule.h
+++ b/src/nodes/averageMolecule.h
@@ -8,6 +8,7 @@
 #include "nodes/node.h"
 
 // Forward Declarations
+class Configuration;
 class SpeciesSite;
 
 class AverageMoleculeNode : public Node
diff --git a/src/nodes/axisAngle.h b/src/nodes/axisAngle.h
index cb53728f52..e8b6d22dc7 100644
--- a/src/nodes/axisAngle.h
+++ b/src/nodes/axisAngle.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include "classes/site.h"
 #include "classes/speciesSites.h"
 #include "math/histogram1D.h"
 #include "math/histogram2D.h"
@@ -10,6 +11,7 @@
 #include "nodes/node.h"
 
 // Forward Declarations
+class Configuration;
 class SpeciesSite;
 
 class AxisAngleNode : public Node
diff --git a/src/nodes/bragg.cpp b/src/nodes/bragg.cpp
index eecec5ac04..425940dffe 100644
--- a/src/nodes/bragg.cpp
+++ b/src/nodes/bragg.cpp
@@ -4,6 +4,7 @@
 #define _USE_MATH_DEFINES
 #include "nodes/bragg.h"
 #include "base/timer.h"
+#include "classes/atomType.h"
 #include "classes/partialSet.h"
 
 BraggNode::BraggNode(Graph *parentGraph)
diff --git a/src/nodes/bragg.h b/src/nodes/bragg.h
index 81940bf28c..35ff3e148e 100644
--- a/src/nodes/bragg.h
+++ b/src/nodes/bragg.h
@@ -6,6 +6,7 @@
 #include "classes/braggReflection.h"
 #include "classes/configuration.h"
 #include "classes/kVector.h"
+#include "math/function1D.h"
 #include "math/history.h"
 #include "nodes/node.h"
 
diff --git a/src/nodes/cif/importCIFStructure.cpp b/src/nodes/cif/importCIFStructure.cpp
index 53bad76aef..20c7e9d3ad 100644
--- a/src/nodes/cif/importCIFStructure.cpp
+++ b/src/nodes/cif/importCIFStructure.cpp
@@ -6,7 +6,6 @@
 #include "CIFImportParser.h"
 #include "base/messenger.h"
 #include "base/sysFunc.h"
-#include "classes/coreData.h"
 #include "classes/empiricalFormula.h"
 #include "nodes/cif/io/CIFImportErrorListeners.h"
 #include "nodes/cif/io/CIFImportVisitor.h"
diff --git a/src/nodes/dAngle.h b/src/nodes/dAngle.h
index 117c0e069f..fa23c72d7d 100644
--- a/src/nodes/dAngle.h
+++ b/src/nodes/dAngle.h
@@ -9,6 +9,9 @@
 #include "math/rangedVector3.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class DAngleNode : public Node
 {
     public:
diff --git a/src/nodes/dissolve.cpp b/src/nodes/dissolve.cpp
index 59c640735e..2ded84037b 100644
--- a/src/nodes/dissolve.cpp
+++ b/src/nodes/dissolve.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/dissolve.h"
+#include "classes/configuration.h"
 #include "classes/potentialMap.h"
 #include "kernels/energy.h"
 #include "kernels/force.h"
diff --git a/src/nodes/dissolve.h b/src/nodes/dissolve.h
index 7128b45e15..7cb6d82658 100644
--- a/src/nodes/dissolve.h
+++ b/src/nodes/dissolve.h
@@ -11,6 +11,7 @@
 #include <filesystem>
 
 // Forward declarations
+class Configuration;
 class EnergyKernel;
 class ForceKernel;
 class PotentialMap;
diff --git a/src/nodes/energy.cpp b/src/nodes/energy.cpp
index b43f56aba2..6b8310c45c 100644
--- a/src/nodes/energy.cpp
+++ b/src/nodes/energy.cpp
@@ -3,6 +3,7 @@
 
 #include "nodes/energy.h"
 #include "base/timer.h"
+#include "classes/configuration.h"
 #include "kernels/energy.h"
 #include "math/regression.h"
 #include "nodes/dissolve.h"
diff --git a/src/nodes/energy.h b/src/nodes/energy.h
index 1e345c578c..32a577147c 100644
--- a/src/nodes/energy.h
+++ b/src/nodes/energy.h
@@ -6,6 +6,9 @@
 #include "math/history.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class EnergyNode : public Node
 {
     public:
diff --git a/src/nodes/epsr.cpp b/src/nodes/epsr.cpp
index 350c973b55..8c1e22d3ce 100644
--- a/src/nodes/epsr.cpp
+++ b/src/nodes/epsr.cpp
@@ -3,6 +3,7 @@
 
 #include "nodes/epsr.h"
 #include "base/sysFunc.h"
+#include "classes/configuration.h"
 #include "classes/partialSet.h"
 #include "classes/scatteringMatrix.h"
 #include "main/dissolve.h"
diff --git a/src/nodes/epsr.h b/src/nodes/epsr.h
index fa65453c3a..c4ad73ba0e 100644
--- a/src/nodes/epsr.h
+++ b/src/nodes/epsr.h
@@ -16,6 +16,7 @@
 
 // Forward Declarations
 class AtomType;
+class Configuration;
 class PartialSet;
 
 class EPSRNamedTargetWeights : public Serialisable
diff --git a/src/nodes/exportDLPOLYConfiguration.cpp b/src/nodes/exportDLPOLYConfiguration.cpp
index 39f27a4f72..015a0a11a5 100644
--- a/src/nodes/exportDLPOLYConfiguration.cpp
+++ b/src/nodes/exportDLPOLYConfiguration.cpp
@@ -2,8 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/exportDLPOLYConfiguration.h"
+#include "classes/atomType.h"
+#include "classes/configuration.h"
 #include "data/atomicMasses.h"
-#include "main/dissolve.h"
 #include "nodes/constants.h"
 #include <fstream>
 
diff --git a/src/nodes/exportXYZConfiguration.cpp b/src/nodes/exportXYZConfiguration.cpp
index 7d3eea8702..c5594acc70 100644
--- a/src/nodes/exportXYZConfiguration.cpp
+++ b/src/nodes/exportXYZConfiguration.cpp
@@ -2,7 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/exportXYZConfiguration.h"
-#include "main/dissolve.h"
+#include "classes/configuration.h"
 #include "nodes/constants.h"
 #include <fstream>
 
diff --git a/src/nodes/exportXYZTrajectory.cpp b/src/nodes/exportXYZTrajectory.cpp
index f322ff5344..6eb8fc9a69 100644
--- a/src/nodes/exportXYZTrajectory.cpp
+++ b/src/nodes/exportXYZTrajectory.cpp
@@ -2,6 +2,8 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/exportXYZTrajectory.h"
+#include "classes/atomType.h"
+#include "classes/configuration.h"
 #include <fstream>
 
 ExportXYZTrajectoryNode::ExportXYZTrajectoryNode(Graph *parentGraph) : Node(parentGraph)
diff --git a/src/nodes/exportXYZTrajectory.h b/src/nodes/exportXYZTrajectory.h
index 7b65f9dfe7..4b4e3d6e20 100644
--- a/src/nodes/exportXYZTrajectory.h
+++ b/src/nodes/exportXYZTrajectory.h
@@ -30,7 +30,7 @@ class ExportXYZTrajectoryNode : public Node
     // File path
     std::string filePath_;
     // File format
-    bool extended_;
+    bool extended_{false};
     // Last read file position
     std::streampos filePosition_;
     // Target configuration
diff --git a/src/nodes/histogramCN.h b/src/nodes/histogramCN.h
index 29d2a52f9e..d44c3087c4 100644
--- a/src/nodes/histogramCN.h
+++ b/src/nodes/histogramCN.h
@@ -8,6 +8,9 @@
 #include "math/range.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 // Histogrammed Coordination Numbers
 class HistogramCNNode : public Node
 {
diff --git a/src/nodes/importDLPOLYStructure.h b/src/nodes/importDLPOLYStructure.h
index cefb1d0b21..bdb96ad97b 100644
--- a/src/nodes/importDLPOLYStructure.h
+++ b/src/nodes/importDLPOLYStructure.h
@@ -5,6 +5,7 @@
 
 #include "classes/structure.h"
 #include "nodes/node.h"
+#include "templates/optionalRef.h"
 
 class ImportDLPOLYStructureNode : public Node
 {
diff --git a/src/nodes/insert.h b/src/nodes/insert.h
index 587d4b88b1..580588d899 100644
--- a/src/nodes/insert.h
+++ b/src/nodes/insert.h
@@ -7,6 +7,9 @@
 #include "classes/moleculeSet.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class InsertNode : public Node
 {
     public:
diff --git a/src/nodes/intraAngle.h b/src/nodes/intraAngle.h
index 5329664170..6cda1eb385 100644
--- a/src/nodes/intraAngle.h
+++ b/src/nodes/intraAngle.h
@@ -8,6 +8,9 @@
 #include "math/range.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class IntraAngleNode : public Node
 {
     public:
diff --git a/src/nodes/intraDistance.h b/src/nodes/intraDistance.h
index dc2bd1e9af..92c82b6775 100644
--- a/src/nodes/intraDistance.h
+++ b/src/nodes/intraDistance.h
@@ -7,6 +7,9 @@
 #include "math/histogram1D.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class IntraDistanceNode : public Node
 {
     public:
diff --git a/src/nodes/modifierOSites.h b/src/nodes/modifierOSites.h
index dd46fe0590..b6af22be7b 100644
--- a/src/nodes/modifierOSites.h
+++ b/src/nodes/modifierOSites.h
@@ -9,6 +9,9 @@
 #include "math/range.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class ModifierOSitesNode : public Node
 {
     public:
diff --git a/src/nodes/moleculeTorsion.h b/src/nodes/moleculeTorsion.h
index 68b53c20ca..42720c0d62 100644
--- a/src/nodes/moleculeTorsion.h
+++ b/src/nodes/moleculeTorsion.h
@@ -6,6 +6,9 @@
 #include "math/histogram1D.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class MoleculeTorsionNode : public Node
 {
     public:
diff --git a/src/nodes/neutronSQ.h b/src/nodes/neutronSQ.h
index 7c034e5898..5067b31914 100644
--- a/src/nodes/neutronSQ.h
+++ b/src/nodes/neutronSQ.h
@@ -10,6 +10,9 @@
 #include "nodes/node.h"
 #include <optional>
 
+// Forward Declarations
+class Configuration;
+
 class NeutronSQNode : public Node
 {
     public:
diff --git a/src/nodes/node.h b/src/nodes/node.h
index 6708a4d5ad..778a9d8b17 100644
--- a/src/nodes/node.h
+++ b/src/nodes/node.h
@@ -18,6 +18,7 @@
 #include <vector>
 
 // Forward Declarations
+class AtomType;
 class Graph;
 class Edge;
 class DissolveGraph;
diff --git a/src/nodes/orientedSDF.h b/src/nodes/orientedSDF.h
index c4833885cd..b5f4e3751e 100644
--- a/src/nodes/orientedSDF.h
+++ b/src/nodes/orientedSDF.h
@@ -3,12 +3,15 @@
 
 #pragma once
 
+#include "classes/site.h"
 #include "classes/speciesSites.h"
 #include "math/histogram3D.h"
 #include "math/range.h"
 #include "nodes/node.h"
 
-// OrientedSDF
+// Forward Declarations
+class Configuration;
+
 class OrientedSDFNode : public Node
 {
     public:
diff --git a/src/nodes/parameter.h b/src/nodes/parameter.h
index c50b71b7ea..a925056362 100644
--- a/src/nodes/parameter.h
+++ b/src/nodes/parameter.h
@@ -6,7 +6,6 @@
 #include "base/context.h"
 #include "base/enumOptions.h"
 #include "base/serialiser.h"
-#include "classes/coreData.h"
 #include "math/data1D.h"
 #include "nodes/number.h"
 #include "templates/algorithms.h"
diff --git a/src/nodes/qSpecies.h b/src/nodes/qSpecies.h
index 4bd77c420c..0906b25225 100644
--- a/src/nodes/qSpecies.h
+++ b/src/nodes/qSpecies.h
@@ -4,12 +4,13 @@
 #pragma once
 
 #include "classes/speciesSites.h"
-#include "math/histogram1D.h"
 #include "math/integerHistogram1D.h"
 #include "math/range.h"
 #include "nodes/node.h"
 
-// Q-Species
+// Forward Declarations
+class Configuration;
+
 class QSpeciesNode : public Node
 {
     public:
diff --git a/src/nodes/sdf.h b/src/nodes/sdf.h
index efaf494abd..05f8a8765e 100644
--- a/src/nodes/sdf.h
+++ b/src/nodes/sdf.h
@@ -7,7 +7,9 @@
 #include "math/histogram3D.h"
 #include "nodes/node.h"
 
-// SDF
+// Forward Declarations
+class Configuration;
+
 class SDFNode : public Node
 {
     public:
diff --git a/src/nodes/setCoordinates.cpp b/src/nodes/setCoordinates.cpp
index bc40846807..06b83b4ca5 100644
--- a/src/nodes/setCoordinates.cpp
+++ b/src/nodes/setCoordinates.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/setCoordinates.h"
+#include "classes/configuration.h"
 
 SetCoordinatesNode::SetCoordinatesNode(Graph *parentGraph) : Node(parentGraph)
 {
diff --git a/src/nodes/sq.h b/src/nodes/sq.h
index 396cfcfc24..e1f81b12c7 100644
--- a/src/nodes/sq.h
+++ b/src/nodes/sq.h
@@ -9,6 +9,9 @@
 #include "math/windowFunction.h"
 #include "nodes/node.h"
 
+// Forward Declarations
+class Configuration;
+
 class SQNode : public Node
 {
     public:
diff --git a/src/nodes/voxelDensity.cpp b/src/nodes/voxelDensity.cpp
index 60b55b66cd..3aa38d1a09 100644
--- a/src/nodes/voxelDensity.cpp
+++ b/src/nodes/voxelDensity.cpp
@@ -2,9 +2,9 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "nodes/voxelDensity.h"
-#include "analyser/dataExporter.h"
 #include "analyser/dataOperator1D.h"
 #include "data/atomicMasses.h"
+#include "data/isotopes.h"
 
 VoxelDensityNode::VoxelDensityNode(Graph *parentGraph) : Node(parentGraph)
 {
diff --git a/src/nodes/voxelDensity.h b/src/nodes/voxelDensity.h
index 6884a06147..c81c4b6444 100644
--- a/src/nodes/voxelDensity.h
+++ b/src/nodes/voxelDensity.h
@@ -8,6 +8,7 @@
 #include "templates/array3D.h"
 
 // Forward declarations
+class Box;
 class Configuration;
 
 class VoxelDensityNode : public Node
diff --git a/src/nodes/xRaySQ.h b/src/nodes/xRaySQ.h
index 94a30d76b3..f1d3ff4723 100644
--- a/src/nodes/xRaySQ.h
+++ b/src/nodes/xRaySQ.h
@@ -12,6 +12,9 @@
 #include "nodes/node.h"
 #include <optional>
 
+// Forward Declarations
+class Configuration;
+
 class XRaySQNode : public Node
 {
     public:
diff --git a/tests/classes/cells2.cpp b/tests/classes/cells2.cpp
index 24122034ef..a68dac9a5f 100644
--- a/tests/classes/cells2.cpp
+++ b/tests/classes/cells2.cpp
@@ -2,6 +2,7 @@
 // Copyright (c) 2026 Team Dissolve and contributors
 
 #include "classes/atomType.h"
+#include "classes/configuration.h"
 #include "classes/species.h"
 #include "main/dissolve.h"
 #include "math/mathFunc.h"
diff --git a/tests/gui/masterTerms.cpp b/tests/gui/masterTerms.cpp
index 0c8123a4af..e2d217aac1 100644
--- a/tests/gui/masterTerms.cpp
+++ b/tests/gui/masterTerms.cpp
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Copyright (c) 2026 Team Dissolve and contributors
 
+#include "classes/species.h"
 #include "gui/models/commonAngleModel.h"
 #include "gui/models/commonBondModel.h"
 #include "gui/models/commonTorsionModel.h"
@@ -13,7 +14,6 @@
 
 namespace UnitTest
 {
-
 class MasterTermsTableModelTest : public ::testing::Test
 {
     public:
diff --git a/tests/gui/optionalDoubleKeyword.cpp b/tests/gui/optionalDoubleKeyword.cpp
index 9f66f1c2a1..ee9a3d34f7 100644
--- a/tests/gui/optionalDoubleKeyword.cpp
+++ b/tests/gui/optionalDoubleKeyword.cpp
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Copyright (c) 2026 Team Dissolve and contributors
 
-#include "classes/coreData.h"
 #include "gui/keywordWidgets/optionalDouble.h"
 #include <QApplication>
 #include <gtest/gtest.h>
diff --git a/tests/gui/optionalIntegerKeyword.cpp b/tests/gui/optionalIntegerKeyword.cpp
index 814630c537..b7400b7d6c 100644
--- a/tests/gui/optionalIntegerKeyword.cpp
+++ b/tests/gui/optionalIntegerKeyword.cpp
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // Copyright (c) 2026 Team Dissolve and contributors
 
-#include "classes/coreData.h"
 #include "gui/keywordWidgets/optionalInt.h"
 #include <QApplication>
 #include <gtest/gtest.h>
diff --git a/tests/gui/xmlForcefield.cpp b/tests/gui/xmlForcefield.cpp
index 5e7a970cf8..d462699f5b 100644
--- a/tests/gui/xmlForcefield.cpp
+++ b/tests/gui/xmlForcefield.cpp
@@ -145,8 +145,7 @@ TEST_F(XmlFFTest, XmlImproper)
 
 TEST_F(XmlFFTest, XmlAtom)
 {
-    CoreData coreData;
-    XmlAtomModel atoms(coreData);
+    XmlAtomModel atoms;
 
     atoms.readFile(doc.root());
 
@@ -176,8 +175,7 @@ TEST_F(XmlFFTest, XmlAtom)
 
 TEST_F(XmlFFTest, XmlTree)
 {
-    CoreData coreData;
-    XmlTreeModel treeModel(coreData);
+    XmlTreeModel treeModel;
 
     treeModel.setName("TestFF");
 
diff --git a/tests/nodes/graph.cpp b/tests/nodes/graph.cpp
index cd3588adfd..5e686a9387 100644
--- a/tests/nodes/graph.cpp
+++ b/tests/nodes/graph.cpp
@@ -67,8 +67,7 @@ TEST_F(GraphCoreTest, Serialisation)
 {
     createGraph();
 
-    CoreData cd;
-    Dissolve d(cd);
+    Dissolve d;
     DissolveGraph copy;
     auto serialised = root_.into_toml();
 
diff --git a/tests/nodes/loop.cpp b/tests/nodes/loop.cpp
index 130af24d40..27b784b671 100644
--- a/tests/nodes/loop.cpp
+++ b/tests/nodes/loop.cpp
@@ -74,8 +74,7 @@ class IterableGraphTest : public ::testing::Test
 
 TEST_F(IterableGraphTest, BasicNonLoopingSeries)
 {
-    CoreData coreData;
-    Dissolve dissolve(coreData);
+    Dissolve dissolve;
     auto root = std::make_unique<DissolveGraph>();
     auto loop = dynamic_cast<IterableGraph *>(root->createNode("Iterator", "Iterator"));
     auto i = dynamic_cast<NumberNode *>(root->createNode("Number", "i"));
diff --git a/tests/testData.h b/tests/testData.h
index 447f58e191..3bb78b255d 100644
--- a/tests/testData.h
+++ b/tests/testData.h
@@ -3,7 +3,6 @@
 
 #pragma once
 
-#include "classes/coreData.h"
 #include "classes/partialSet.h"
 #include "classes/species.h"
 #include "kernels/energy.h"
@@ -99,13 +98,12 @@ template <class T> void tomlRoundTrip(T &a, T &b)
 class DissolveSystemTest
 {
     public:
-    DissolveSystemTest() : dissolve_(coreData_) { dissolve_.setRestartFileFrequency(0); };
+    DissolveSystemTest() { dissolve_.setRestartFileFrequency(0); };
 
     /*
      * Dissolve & CoreData
      */
     private:
-    CoreData coreData_;
     Dissolve dissolve_;
     // Whether to perform rewrite checks on setUp
     bool rewriteCheck_{true};
@@ -115,8 +113,6 @@ class DissolveSystemTest
     public:
     // Return the Dissolve object
     Dissolve &dissolve() { return dissolve_; }
-    // Return the CoreData object
-    CoreData &coreData() { return coreData_; }
 
     /*
      * Checks