Tutorial 15

🧪 The Materials Project

The Materials Project is a world-leading database of all known materials simulated using VASP. It’s an incredible resource for finding structural, energetic, and electronic properties of materials — both real and hypothetical.

👉 Fun fact: The Materials Project is built using pymatgen!
We’ll use pymatgen ourselves in this tutorial to explore case studies and automate our own workflows.

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🔑 Get Your API Key

To interact with the Materials Project programmatically, you need your personal API key.

📋 Steps:

1. Go to https://next-gen.materialsproject.org/
2. Create an account or log in.
3. Click the “👤 API” button in the top-right corner.
4. Copy your API Key — a long string of letters and numbers.
5. Keep it safe! Don’t share your key publicly.

Once you have your key, you can begin querying the Materials Project using Python.

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🔍 Querying the Materials Project

Here’s an example of how to use pymatgen to search for stable oxygen-containing compounds that are known from experiments and have small-to-moderate unit cells:

from mp_api.client import MPRester

API_KEY = '<YOUR API KEY>'  # Replace with your actual API key

with MPRester(API_KEY) as mpr:
    docs = mpr.summary.search(
        elements=["O"],              # Must contain Oxygen
        is_stable=True,              # Thermodynamically stable
        theoretical=False,           # Reported from experiment
        nsites=["1", "40"],          # Unit cell has 1–40 atoms
        fields=["material_id"]       # Only return material IDs
    )

with open('result.txt', 'w') as f:
    for doc in docs:
        f.write(f"{doc.material_id}\n")

📂 This script will:

• Query the database
• Filter results based on your criteria
• Write all matching mp-ids to result.txt

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⚙️ Automatically Create VASP Input Files

Now that you’ve downloaded some material IDs from the Materials Project, let’s generate full VASP input folders for each one:

from mp_api.client import MPRester
from pymatgen.io.vasp.inputs import Poscar
from pymatgen.io.vasp.sets import MPRelaxSet
import os

API_KEY = '<YOUR API KEY>'  # Replace with your real key

# Load list of material IDs
with open('result.txt') as f:
    lines = f.read().splitlines()

# Optionally sort or preprocess lines if needed
newlines = [line.split() for line in lines]
newlines.sort(key=lambda x: int(x[1]))

# Create VASP input sets
for newline in newlines:
    with MPRester(API_KEY) as mpr:
        struct = mpr.get_structure_by_material_id(newline[0])
        poscar = Poscar(structure=struct, comment=newline[0])
        print(poscar)
        try:
            os.makedirs(newline[0])
        except:
            pass
        relax_set = MPRelaxSet(structure=struct)
        relax_set.write_input(output_dir="./" + newline[0])

This script: ✅ Downloads the structure
✅ Creates a POSCAR
✅ Builds a full INCAR, KPOINTS, POTCAR, and POSCAR in a folder named after the material ID

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🎉 Congratulations! You’ve learned how to use the Materials Project API and generate ready-to-run VASP jobs!

👉 You’re now ready for Tutorial 16!