First-principles calculation

A computational method that predicts material properties from quantum mechanics without fitted empirical parameters. It commonly uses approximations to make the quantum equations tractable.

Density functional theory: A quantum-mechanical method that calculates electronic structure using electron density rather than a many-electron wavefunction. It is the most widely used framework for first-principles calculations of materials.
Schrödinger equation: The fundamental equation governing the quantum-mechanical state and evolution of nonrelativistic systems. First-principles methods derive material predictions from its many-particle form.
Crystal structure prediction: The computational search for stable or metastable arrangements of atoms in crystalline solids. Calculated energies help rank candidate structures before experimental synthesis.
Empirical potential: A model of interatomic forces whose parameters are fitted to experimental data or higher-level calculations. Unlike a first-principles calculation, its predictions depend directly on fitted interaction parameters.
Materials Project: An open database and computational platform providing calculated properties for inorganic materials. Its entries make first-principles results available for broad comparison and materials screening.
Born–Oppenheimer approximation: An approximation that separates electronic and nuclear motion because nuclei are much heavier than electrons. It lets calculations treat atomic positions as fixed while solving for electrons.
Periodic boundary conditions: A computational condition that repeats a finite simulation cell indefinitely in space. They let a small crystal cell represent an extended solid.
Phonon: A quantized collective vibration of atoms in a crystal. First-principles force calculations can predict vibrational modes and related thermal properties.
Tight-binding model: An electronic-structure model that represents electrons in localized orbitals with simplified, often fitted interactions. It is usually less computationally demanding but relies on a reduced description.
Open Quantum Materials Database: A database of materials properties computed using quantum-mechanical methods. It exemplifies the accumulation of systematic calculations into a searchable research resource.

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