Source code for

IO support for the Gaussian cube format.

See the format specifications on:

import time

import numpy as np

from ase.atoms import Atoms
from import read
from ase.units import Bohr

ATOMS = 'atoms'
CASTEP = 'castep'
DATA = 'data'

[docs]def write_cube(file_obj, atoms, data=None, origin=None, comment=None): """Function to write a cube file. file_obj: str or file object File to which output is written. atoms: Atoms The Atoms object specifying the atomic configuration. data : 3-dim numpy array, optional (default = None) Array containing volumetric data as e.g. electronic density origin : 3-tuple Origin of the volumetric data (units: Angstrom) comment : str, optional (default = None) Comment for the first line of the cube file. """ if data is None: data = np.ones((2, 2, 2)) data = np.asarray(data) if data.dtype == complex: data = np.abs(data) if comment is None: comment = "Cube file from ASE, written on " + time.strftime("%c") else: comment = comment.strip() file_obj.write(comment) file_obj.write("\nOUTER LOOP: X, MIDDLE LOOP: Y, INNER LOOP: Z\n") if origin is None: origin = np.zeros(3) else: origin = np.asarray(origin) / Bohr file_obj.write( "{0:5}{1:12.6f}{2:12.6f}{3:12.6f}\n".format( len(atoms), *origin)) for i in range(3): n = data.shape[i] d = atoms.cell[i] / n / Bohr file_obj.write("{0:5}{1:12.6f}{2:12.6f}{3:12.6f}\n".format(n, *d)) positions = atoms.positions / Bohr numbers = atoms.numbers for Z, (x, y, z) in zip(numbers, positions): file_obj.write( "{0:5}{1:12.6f}{2:12.6f}{3:12.6f}{4:12.6f}\n".format( Z, 0.0, x, y, z) ) data.tofile(file_obj, sep="\n", format="%e")
[docs]def read_cube(file_obj, read_data=True, program=None, verbose=False): """Read atoms and data from CUBE file. file_obj : str or file Location to the cube file. read_data : boolean If set true, the actual cube file content, i.e. an array containing the electronic density (or something else )on a grid and the dimensions of the corresponding voxels are read. program: str Use program='castep' to follow the PBC convention that first and last voxel along a direction are mirror images, thus the last voxel is to be removed. If program=None, the routine will try to catch castep files from the comment lines. verbose : bool Print some more information to stdout. Returns a dict with the following keys: * 'atoms': Atoms object * 'data' : (Nx, Ny, Nz) ndarray * 'origin': (3,) ndarray, specifying the cube_data origin. * 'spacing': (3, 3) ndarray, representing voxel size """ readline = file_obj.readline line = readline() # the first comment line line = readline() # the second comment line # The second comment line *CAN* contain information on the axes # But this is by far not the case for all programs axes = [] if "OUTER LOOP" in line.upper(): axes = ["XYZ".index(s[0]) for s in line.upper().split()[2::3]] if not axes: axes = [0, 1, 2] # castep2cube files have a specific comment in the second line ... if "castep2cube" in line: program = CASTEP if verbose: print("read_cube identified program: castep") # Third line contains actual system information: line = readline().split() num_atoms = int(line[0]) # num_atoms can be negative. # Negative num_atoms indicates we have extra data to parse after # the coordinate information. has_labels = num_atoms < 0 num_atoms = abs(num_atoms) # There is an optional last field on this line which indicates # the number of values at each point. It is typically 1 (the default) # in which case it can be omitted, but it may also be > 1, # for example if there are multiple orbitals stored in the same cube. num_val = int(line[4]) if len(line) == 5 else 1 # Origin around which the volumetric data is centered # (at least in FHI aims): origin = np.array([float(x) * Bohr for x in line[1:4:]]) cell = np.empty((3, 3)) shape = [] spacing = np.empty((3, 3)) # The upcoming three lines contain the cell information for i in range(3): n, x, y, z = [float(s) for s in readline().split()] shape.append(int(n)) # different PBC treatment in castep, basically the last voxel row is # identical to the first one if program == CASTEP: n -= 1 cell[i] = n * Bohr * np.array([x, y, z]) spacing[i] = np.array([x, y, z]) * Bohr pbc = [(v != 0).any() for v in cell] numbers = np.empty(num_atoms, int) positions = np.empty((num_atoms, 3)) for i in range(num_atoms): line = readline().split() numbers[i] = int(line[0]) positions[i] = [float(s) for s in line[2:]] positions *= Bohr atoms = Atoms(numbers=numbers, positions=positions, cell=cell, pbc=pbc) # CASTEP will always have PBC, although the cube format does not # contain this kind of information if program == CASTEP: atoms.pbc = True dct = {ATOMS: atoms} labels = [] # If we originally had a negative num_atoms, parse the extra fields now. # The first field of the first line tells us how many other fields there # are to parse, but we have to guess how many rows this information is # split over. if has_labels: # Can't think of a more elegant way of doing this... fields = readline().split() nfields = int(fields[0]) labels.extend(fields[1:]) while len(labels) < nfields: fields = readline().split() labels.extend(fields) labels = [int(x) for x in labels] if read_data: # Cube files can contain more than one density, # so we need to be a little bit careful about where one ends # and the next begins. raw_volume = [float(s) for s in] # Split each value at each point into a separate list. raw_volumes = [np.array(raw_volume[offset::num_val]) for offset in range(0, num_val)] datas = [] # Adjust each volume in turn. for data in raw_volumes: data = data.reshape(shape) if axes != [0, 1, 2]: data = data.transpose(axes).copy() if program == CASTEP: # Due to the PBC applied in castep2cube, the last entry # along each dimension equals the very first one. data = data[:-1, :-1, :-1] datas.append(data) datas = np.array(datas) dct[DATA] = datas[0] dct["origin"] = origin dct["spacing"] = spacing dct["labels"] = labels dct["datas"] = datas return dct
def read_cube_data(filename): """Wrapper function to read not only the atoms information from a cube file but also the contained volumetric data. """ dct = read(filename, format="cube", read_data=True, full_output=True) return dct[DATA], dct[ATOMS]