SymmetryReduceBZ.jl

A Julia package for calculating the irreducible Brillouin zone for 2D or 3D crystal structures.
Author jerjorg
Popularity
2 Stars
Updated Last
1 Year Ago
Started In
July 2020

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SymmetryReduceBZ

The primary purpose of SymmetryReduceBZ is to calculate the irreducible Brillouin zone (IBZ) for crystal structures in 2D or 3D provided the real-space lattice vectors, atom positions, and atom types. It also contains methods for making unit cells primitive and lattice reduction. See the User Guide in the documentation for more details and usage examples in Python.

Installation

SymmetryReduceBZ is a registered Julia package and can be installed using Julia's package manager Pkg.

using Pkg
Pkg.add("SymmetryReduceBZ")

Examples

To calculate the irreducible Brillouin zone, provide the lattice and atomic basis to calc_ibz. The IBZ will be returned as either a convex hull or intersection of half spaces.

import SymmetryReduceBZ.Lattices: genlat_CUB
import SymmetryReduceBZ.Symmetry: calc_ibz
a = 2.0
real_latvecs = genlat_CUB(a)
atom_types = [0,0]
atom_pos = Array([0 0 0; 0.5 0.5 0.5]')
ibzformat = "convex hull"
coordinates = "Cartesian"
makeprim = false
convention = "ordinary"
ibz = calc_ibz(real_latvecs,atom_types,atom_pos,coordinates,ibzformat,
  makeprim,convention)

The arguments for calc_ibz are as follows:

  • real_latvecs: the real-space lattice vectors as columns of a matrix.
  • atom_types: a vector of atom types as integers.
  • atom_pos: the positions of atoms in the crystal structure as columns of a matrix.
  • coordinates: indicates the atoms are in "lattice" or "Cartesian" coordinates.
  • ibzformat: the format of the irreducible Brillouin zone. Options include "convex hull" and "half-space".
  • convention: the convention used to go between real and reciprocal space. The two conventions are "ordinary" (temporal) frequency and "angular" frequency.
  • makeprim: make the unit cell primitive before calculating the IBZ if true.
  • rtol=sqrt(eps(float(maximum(real_latvecs)))): (optional) a relative tolerance for floating-point comparisons.
  • atol=1e-9: (optional) an absolute tolerance for floating-point comparisons.

The vertices of the ibz are accessed with ibz.points[ibz.vertices,:]. The vertices of the IBZ and ibz.points should be the same. The rows of the array are the vertices of the IBZ in Cartesian coordinates. Other attributes of the IBZ are accessible, such as the volume ibz.volume. The faces of the IBZ are calculated with

import SymmetryReduceBZ.Utilities: get_uniquefacets
indices = get_uniquefacets(ibz)
facets = [ibz.points[ind] for ind=indices]

facets is a list of points at the corners of each facet. The function get_uniquefacets returns the indices of points that lie on the same facet. The facets are also available through ibz.simplices as simplices, but often multiple simplices lie on the same facet. See the documentation for SciPy for additional attributes of the IBZ.

The function plot_convexhulls is useful for visualizing the Brillouin zone and irreducible Brillouin zone. The arguments are the same as those from calc_ibz.

import SymmetryReduceBZ.Plotting: plot_convexhulls
import SymmetryReduceBZ.Lattices: genlat_CUB
a = 2.0
real_latvecs = genlat_CUB(a)
atom_types = [0,0]
atom_pos = Array([0 0 0; 0.5 0.5 0.5]')
coordinates = "Cartesian"
makeprim = false
convention = "ordinary"
ax=plot_convexhulls(real_latvecs,atom_types,atom_pos,coordinates,
  makeprim,convention)

IBZ

The functions plot_2Dconvexhull and plot_3Dconvexhull allow greater customization of the appearance of the convex hull.

import SymmetryReduceBZ.Symmetry: calc_bz, calc_ibz
import SymmetryReduceBZ.Plotting: plot_2Dconvexhull
using PyPlot
real_latvecs = [1 0; 0 1]
convention="ordinary"
atom_types=[0]
atom_pos = Array([0 0]')
coords = "Cartesian"
ibzformat = "convex hull"
makeprim=false
bz = calc_bz(real_latvecs,atom_types,atom_pos,coords,ibzformat,makeprim,convention)
ibz = calc_ibz(real_latvecs,atom_types,atom_pos,coords,ibzformat,makeprim,convention)
ax = plot_2Dconvexhull(bz,facecolor="deepskyblue",linewidth=3,edgecolor="cyan",alpha=0.2)
ax = plot_2Dconvexhull(ibz,ax;facecolor="coral",linewidth=3,edgecolor="magenta",alpha=0.4)
axis("off")

IBZ

import SymmetryReduceBZ.Symmetry: calc_bz, calc_ibz
import SymmetryReduceBZ.Plotting: plot_3Dconvexhull
using PyPlot
real_latvecs = [1 0 0; 0 1 0; 0 0 1]
convention="ordinary"
atom_types=[0]
atom_pos = Array([0 0 0]')
coords = "Cartesian"
bzformat = "convex hull"
makeprim=false
bz = calc_bz(real_latvecs,atom_types,atom_pos,coords,bzformat,makeprim,convention)
ibz = calc_ibz(real_latvecs,atom_types,atom_pos,coords,bzformat,makeprim,convention)
fig = figure()
ax = fig.add_subplot(111, projection="3d")
ax = plot_3Dconvexhull(ibz,ax,facecolors="pink",alpha=1,edgecolors="black",linewidths = 1)
ax = plot_3Dconvexhull(bz,ax,facecolors="deepskyblue",edgecolors="white",linewidths=1,alpha=0.2)
axis("off")

IBZ

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