Command line

minelastic info | generate | collect | vasp-tensor   [--help for the options of each]

minelastic info

Shows the symmetry, the tensor form and the strain set of a structure, without writing anything.

minelastic info POSCAR                      # any file ASE can read (--format to force a format)
minelastic info --code vasp ref/            # template directory (vasp, aims) or pw.x input (qe)

minelastic generate CODE TEMPLATE

Writes one input directory per strain state, plus STATES and minelastic.json.

CODE	TEMPLATE
vasp	directory with POSCAR, INCAR, POTCAR and KPOINTS (or KSPACING in the INCAR)
qe	pw.x input file
aims	directory with geometry.in and control.in
abinit	directory with POSCAR and one input *.abi that reads it with structure "poscar:POSCAR"
generic	structure file; needs --filename (and --format unless ASE can tell the format from the file name)

option	meaning
-o, --out DIR	output directory (default elastic)
--relax-ions	relax the ions in each strained cell (relaxed-ion constants)
--ionic	also displace the symmetry-irreducible atoms (relaxed-ion and piezoelectric response from clamped cells)
--displacement A	--ionic: atomic step in Å (default 0.01)
--md	fixed-cell molecular dynamics in each strained cell, as set up in the template (finite temperature); vasp and qe
--scheme minimal\|asess	minimal uncoupled set (default) or the six single-component strains
--delta D	strain step (default 0.01)
--stencil four-point\|central\|forward	finite-difference formula (default four-point, \(\pm\delta\) and \(\pm 2\delta\); central with --md)
--symprec S	spglib tolerance in Å (default 1e-5)
--frame auto\|input\|standard	orientation of the applied strains (Conventions)
--potcar copy\|link	vasp: copy or symlink the POTCAR
--fix-incar	vasp: apply all recommended settings the INCAR does not meet (EDIFF, ENCUT, PREC, LREAL); without it they are only reported (The INCAR)
--format FMT, --filename NAME, --extra FILES	generic: ASE format, structure file name, further files to copy

minelastic collect [DIR]

Reads the finished calculations in DIR (default elastic), prints the results and writes DIR/elastic.json.

option	meaning
--method uncoupled\|designated\|lstsq	extraction method (Method)
--output NAME	output file in each directory (defaults: vasprun.xml, then OUTCAR; pw.out; aims.out; newest *.abo)
--format FMT	generic: ASE format of the output file
--internal-strain	print the internal-strain tensor (clamped ions)
--piezo	piezoelectric tensor (and Born charges with --ionic) from the Berry-phase dipoles (VASP LCALCPOL)
--born OUTCAR	Born charges and clamped-ion piezoelectric tensor from a VASP LEPSILON/LCALCEPS run
--md, --skip N	average the stress over the MD steps after the first N
--samples GLOB	average the stresses of per-snapshot sub-directories (e.g. 'conf-*')
--kinetic-temperature T	add the ideal-gas term n k_B T (stresses without the kinetic part)
--stress-measure cauchy\|kirchhoff	differentiate \(\sigma\) (default) or \(J\sigma\) (as VASP IBRION = 6)

minelastic vasp-tensor OUTCAR

Converts the tensor printed by VASP IBRION = 6, ISIF >= 3 to GPa and Voigt order. --which total|clamped|ionic selects TOTAL ELASTIC MODULI (default), SYMMETRIZED ELASTIC MODULI or the ionic relaxation contribution. For the first two it also prints the Born stability and, for a stable tensor, the Voigt-Reuss-Hill moduli.

Output files

file	content
STATES	the strain-state directory names, one per line (for job arrays)
minelastic.json	the setup: program name, version and URL, reference structure, frame rotation, patterns, step, finite-difference multipliers, states, code, template; collect needs it
elastic.json	the results, described below

elastic.json holds:

• always: program, version and url of minelastic, constants (GPa), the matrices C (working frame) and C_input_frame, checks (every stress component with its computed and fitted value), properties (VRH moduli, Young's modulus, Poisson's ratio, anisotropy index; null if C is not positive definite), spacegroup, elastic_type and the collect options;
• errors: standard errors, for MD or snapshot averages with at least two samples per state;
• internal_strain_eV_per_A (N, 3, 6): with the forces of clamped cells;
• piezoelectric_C_per_m2 (3, 6): with the dipoles of the strained cells;
• with --ionic: force_constants_eV_per_A2, internal_strain_displaced_eV_per_A, C_ionic, C_relaxed, ionic_relaxation_A_per_strain, and properties_relaxed if the relaxed-ion C is positive definite. With dipoles or --born also born_charges, born_source, piezoelectric_ionic_C_per_m2, piezoelectric_total_C_per_m2 and piezoelectric_d_pC_per_N.

The same tensors rotated to the orientation of the input structure (identical to the working frame when the cell was not rotated) are C_input_frame, C_relaxed_input_frame, C_ionic_input_frame, internal_strain_input_frame, internal_strain_displaced_input_frame, force_constants_input_frame, ionic_relaxation_input_frame, born_charges_input_frame, piezoelectric_input_frame, piezoelectric_ionic_input_frame, piezoelectric_total_input_frame and piezoelectric_d_input_frame.