pymatgen.analysis.elasticity.stress module

This module provides the Stress class used to create, manipulate, and calculate relevant properties of the stress tensor.

class Stress[source]

Bases: pymatgen.core.tensors.SquareTensor

This class extends SquareTensor as a representation of the stress

Create a Stress object. Note that the constructor uses __new__ rather than __init__ according to the standard method of subclassing numpy ndarrays.

Parameters:stress_matrix (3x3 array-like) – the 3x3 array-like representing the stress

returns the principal invariants of the deviatoric stress tensor, which is calculated by finding the coefficients of the characteristic polynomial of the stress tensor minus the identity times the mean stress


returns the deviatoric component of the stress


returns the mean stress


calculates the first Piola-Kirchoff stress

Parameters:def_grad (3x3 array-like) – deformation gradient tensor

calculates the second Piola-Kirchoff stress

Parameters:def_grad (3x3 array-like) – rate of deformation tensor
symbol = 's'

returns the von mises stress