From daf33ced67f295287184b211f6ab95070c6ca42f Mon Sep 17 00:00:00 2001
From: Troy Smith <troy.smith@uga.edu>
Date: Sat, 2 May 2026 13:56:48 -0400
Subject: [PATCH 1/2] Fixed ORCA encoder adding "None" when not providing basis
 set

Added test to check "None" is not entered into input file through ORCA encoder.
---
 src/qccodec/encoders/orca.py |  7 ++++++-
 tests/test_orca_encoders.py  | 11 +++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/qccodec/encoders/orca.py b/src/qccodec/encoders/orca.py
index 10c8aaf..b0eeded 100644
--- a/src/qccodec/encoders/orca.py
+++ b/src/qccodec/encoders/orca.py
@@ -96,7 +96,12 @@ def encode(program_input: ProgramInput) -> NativeInput:
         inp_lines.append("")
 
     # Method and Basis
-    inp_lines.append(f"! {program_input.model.method} {program_input.model.basis}")
+    model_line = f"! {program_input.model.method}"
+    # ORCA will not recognize 'None' when using composite methods
+    if program_input.model.basis:
+        model_line += f" {program_input.model.basis}"
+
+    inp_lines.append(model_line)
 
     # NumGrad. May be used for gradients or optimizations
     if "numgrad" in kw_lower:
diff --git a/tests/test_orca_encoders.py b/tests/test_orca_encoders.py
index 8f6a0a3..2cf71ec 100644
--- a/tests/test_orca_encoders.py
+++ b/tests/test_orca_encoders.py
@@ -81,6 +81,17 @@ def test_write_input_files(
                 )
 
 
+def test_no_none_fields():
+    """Tests 'None' not in input file when basis not provided."""
+    program_input = ProgramInput(
+        calctype=CalcType.optimization, model=Model(method="xTB"), structure=water
+    )
+    native_input = encode(program_input)
+    input_file = native_input.input_file
+
+    assert "None" not in input_file, f"'None' found in\n{input_file}"
+
+
 def test_validate_keywords_raises_error_if_coords_block_in_keywords():
     """The 'coords' block should not be set directly as a keyword."""
 

From 00e753ee5dbce9073f06309ca0df123e1e4dfd13 Mon Sep 17 00:00:00 2001
From: Colton Hicks <github@coltonhicks.com>
Date: Sat, 2 May 2026 14:41:29 -0700
Subject: [PATCH 2/2] Added CHANGELOG entry

---
 CHANGELOG.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a7c2f1..3cd2467 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [unreleased]
 
+### Fixed
+
+- ORCA encoder no longer writes `None` if no basis (e.g., when no basis is needed for an XTB calculation). [#42](https://github.com/coltonbh/qccodec/pull/42) by [TroyNSmith](https://github.com/TroyNSmith)
+
 ## [0.10.0] - 2026-03-26
 
 ### Changed