Source code for pymatgen.analysis.piezo

# coding: utf-8
# Copyright (c) Pymatgen Development Team.
# Distributed under the terms of the MIT License.


"""
This module provides classes for the Piezoelectric tensor
"""
from pymatgen.core.tensors import Tensor
import numpy as np
import warnings

__author__ = "Shyam Dwaraknath"
__copyright__ = "Copyright 2016, The Materials Project"
__version__ = "1.0"
__maintainer__ = "Shyam Dwaraknath"
__email__ = "shyamd@lbl.gov"
__status__ = "Development"
__date__ = "Feb, 2016"


[docs]class PiezoTensor(Tensor): """ This class describes the 3x6 piezo tensor in Voigt-notation """ def __new__(cls, input_array, tol=1e-3): """ Create an PiezoTensor object. The constructor throws an error if the shape of the input_matrix argument is not 3x3x3, i. e. in true tensor notation. Note that the constructor uses __new__ rather than __init__ according to the standard method of subclassing numpy ndarrays. Args: input_matrix (3x3x3 array-like): the 3x6 array-like representing the piezo tensor """ obj = super().__new__(cls, input_array, check_rank=3) if not (obj - np.transpose(obj, (0, 2, 1)) < tol).all(): warnings.warn("Input piezo tensor does " "not satisfy standard symmetries") return obj.view(cls)
[docs] @classmethod def from_vasp_voigt(cls, input_vasp_array): """ Args: input_vasp_array (nd.array): Voigt form of tensor. Returns: PiezoTensor """ voigt_map = [(0, 0), (1, 1), (2, 2), (0, 1), (1, 2), (0, 2)] input_vasp_array = np.array(input_vasp_array) rank = 3 pt = np.zeros([rank, 3, 3]) for dim in range(rank): for pos in range(len(voigt_map)): pt[dim][voigt_map[pos]] = input_vasp_array[dim][pos] pt[dim].T[voigt_map[pos]] = input_vasp_array[dim][pos] return cls(pt)