Elastic Property Workup

1. Define the strain family explicitly

• Use explicit deformation matrices when the study has a published protocol.
• Use mode/value grids only when the intended strain amplitudes are already justified.
• Record the actual strain amplitudes and matrix convention; “small strain” is not a reproducible input.

2. Choose the evaluation semantics before execution

• For ordinary finite-strain elastic screening, default to strained-structure single-point/stress collection rather than quietly relaxing each strained cell.
• If the scientific protocol requires internal-coordinate relaxation or another non-default treatment, state that explicitly and keep it uniform across the whole set.
• Do not mix fixed-cell stress jobs and relax-style jobs inside one comparison set without separating the results.

3. Keep execution uniform

• Apply one method contract across the whole strain set.
• Keep the same k-point density, ENCUT, spin treatment, DFT+U, and dispersion policy across every strain member.

4. Collect, do not overclaim

• analyze_vasp_results separates failed strain points from usable ones.
• This skill stops at collected energies/forces/stresses; it does not fit elastic constants itself.
• Keep a ledger of which strained member produced usable stress/energy output and which failed.

Method-critical defaults

• Keep the unstrained reference and every strained member on the same magnetic and electronic-structure footing.
• Report the actual strain matrices used; “small strain” is not specific enough for later fitting or reproduction.
• Keep the stress-vs-relax semantics explicit in the final handoff; elastic fitting cannot be audited without that distinction.
• Report the stress/energy units and the reference strain convention together.

Output Contract

Return:

• strained structure batch root
• execution root
• VASP analysis summary path
• explicit strain-matrix ledger
• whether the stage used fixed-cell stress evaluation or an explicitly relaxed protocol

References

• Treat tensor fitting and uncertainty analysis as a downstream analysis stage, not as an implicit promise of this skill.