Elastic Strain

Compute crystal-referenced elastic strain by mapping local environments to an ideal lattice.

Overview

Elastic Strain is the right tool when your system can still be meaningfully compared to an ideal crystal lattice. Instead of comparing a frame to an arbitrary reference configuration, it tries to map local environments onto a chosen crystal structure and then computes elastic strain measures from that mapping.

That makes it a better fit for lattice-referenced deformation analysis than for fully general plastic or highly disordered systems.

Parameters

Parameter	Type	Default	Description
`latticeConstant`	`float`	—	Lattice constant a0. Required.
`crystalStructure`	`string`	`BCC`	Reference crystal structure type. Options: `FCC`, `BCC`, `HCP`, `SC`, `CUBIC_DIAMOND`, `HEX_DIAMOND`.
`caRatio`	`float`	`1.0`	c/a ratio for HCP and hexagonal crystals.
`pushForward`	`bool`	`false`	Push strain to the spatial frame.
`calcDeformationGradient`	`bool`	`true`	Compute deformation gradient `F`.
`calcStrainTensors`	`bool`	`true`	Compute strain tensors.
`identificationMode`	`string`	`PTM`	Structure identification mode. Options: `CNA`, `PTM`.
`rmsd`	`float`	`0.10`	RMSD cutoff for PTM classification.

Practical notes

latticeConstant is mandatory in practice, not just conceptually important.
Atoms that cannot be mapped cleanly to the expected crystal context are emitted with zero-valued strain properties.
This plugin does not perform a full elastic-versus-plastic decomposition in the broad continuum-mechanics sense. It computes elastic strain relative to an ideal lattice when that mapping is possible.

Output

`{outputBase}_elastic_strain.msgpack`

type StrainTensor = [float, float, float, float, float, float];
type DeformationGradient = [float, float, float, float, float, float, float, float, float];

interface PerAtomProperties {
    id: int;
    volumetric_strain: float;
    strain_tensor?: StrainTensor;
    deformation_gradient?: DeformationGradient;
}

interface ElasticStrainOutput {
    main_listing: {
        average_volumetric_strain: float;
    };
    "per-atom-properties": PerAtomProperties[];
}

`{outputBase}_atoms.msgpack`

Grouped atoms by structure family for visualization and downstream context.