Source code for aiida_quantumespresso.calculations.functions.create_kpoints_from_distance

# -*- coding: utf-8 -*-
"""Calculation function to compute a k-point mesh for a structure with a guaranteed minimum k-point distance."""
from aiida.engine import calcfunction


@calcfunction
def create_kpoints_from_distance(structure, distance, force_parity):
    """Generate a uniformly spaced kpoint mesh for a given structure.

    The spacing between kpoints in reciprocal space is guaranteed to be at least the defined distance.

    :param structure: the StructureData to which the mesh should apply
    :param distance: a Float with the desired distance between kpoints in reciprocal space
    :param force_parity: a Bool to specify whether the generated mesh should maintain parity
    :returns: a KpointsData with the generated mesh
    """
    from aiida.orm import KpointsData
    from numpy import linalg

    epsilon = 1E-5

    kpoints = KpointsData()
    kpoints.set_cell_from_structure(structure)
    kpoints.set_kpoints_mesh_from_density(distance.value, force_parity=force_parity.value)

    lengths_vector = [linalg.norm(vector) for vector in structure.cell]
    lengths_kpoint = kpoints.get_kpoints_mesh()[0]

    is_symmetric_cell = all(abs(length - lengths_vector[0]) < epsilon for length in lengths_vector)
    is_symmetric_mesh = all(length == lengths_kpoint[0] for length in lengths_kpoint)

    # If the vectors of the cell all have the same length, the kpoint mesh should be isotropic as well
    if is_symmetric_cell and not is_symmetric_mesh:
        nkpoints = max(lengths_kpoint)
        kpoints.set_kpoints_mesh([nkpoints, nkpoints, nkpoints])

    return kpoints