How to Use Crystal Relaxation

Crystal Relaxation minimizes the predicted potential energy of an ordered bulk inorganic crystal. Upload a CIF and choose atomic-position relaxation with a fixed lattice, or simultaneous atom and cell optimization at the selected external pressure. Choose one of eight methods: MACE-MPA-0 medium, MACE-MP-0b3 medium, conservative Orb-v3 OMat, MatterSim 5M, SevenNet-MF-ompa (mpa), Quantum ESPRESSO PBE, CP2K PBE, or ABINIT PBE. ML potentials use fixed server-selected checkpoints. Quantum ESPRESSO and ABINIT use CC-BY-4.0 PseudoDojo PBE scalar-relativistic standard potentials; CP2K uses its GTH-PBE and DZVP-MOLOPT data. DFT supports at most 128 atoms.

Each selected engine supplies energy, forces, and stress. ML potentials approximate their respective reference datasets. DFT methods evaluate neutral PBE calculations with the selected spin initialization, optional two-body D3(BJ) correction, occupations, and a fixed starting k-point mesh; no Hubbard U, spin-orbit coupling, or magnetic-state search is included. Initial moments are specified per element; antiferromagnetic ordering within an element is unsupported. For plane-wave engines, the requested cutoff is raised to at least the highest PseudoDojo high-accuracy recommendation among the elements. CP2K uses a configurable density grid, default 600 Ry. Automatic optimizer selection uses FIRE for ML potentials and BFGS for DFT; Advanced Settings can override this with either optimizer. For cell relaxation, the optimizer adjusts the lattice through a cell filter. Cell convergence requires the projected force and stress imbalance in allowed atomic and cell directions to meet their tolerances. Target pressure is included in the stress imbalance; shape-preserving relaxation uses its mean normal component. Fixed-cell convergence requires only the force criterion.

CIF symmetry is expanded into the supplied cell before optimization. No primitive-cell conversion is imposed. Symmetry preservation, cell constraints, and frozen atoms are optional Advanced Settings. Symmetry is detected from the starting geometry and may refine small deviations within the selected tolerance; it cannot be combined with frozen atoms or XY/Z-only strain. Partial occupancies and mixed-species sites must be resolved into an ordered structure before submission. Cell heights must be at least 2 Å; lattice-vector lengths must be at most 200 Å.

The relaxed geometry is a local minimum candidate of the selected energy model. It is not proof of synthesizability or an energy-above-hull result. ML-potential results are not DFT calculations. Energies should not be mixed directly with results from other methods or used as Materials Project reference energies. A spin-polarized calculation uses one chosen element-level initialization and does not search magnetic states. D3(BJ), when selected for DFT, adds two-body dispersion consistently to energies, forces, and stress.

• Direct crystal input: Expand CIF symmetry without converting the crystal into a protein representation.
• Explicit convergence: Inspect physical forces and stress alongside the returned geometry.
• Reusable outputs: Carry the relaxed CIF into subsequent materials calculations.