def structure_block(self):
""" Retrieve which CIF block has the appropriate structural information """
blocks = (self.file[key] for key in self.file.keys())
for block in blocks:
try:
_, _ = get_number_with_esd(block["_cell_length_a"])
except KeyError:
continue
else:
return block
def lattice_parameters(self):
"""
Returns the lattice parameters associated to a CIF structure.
Returns
----------
a, b, c : float
Lengths of lattice vectors [Angstroms]
alpha, beta, gamma : float
Angles of lattice vectors [degrees].
"""
block = self.structure_block
try:
a_with_err = block["_cell_length_a"]
except KeyError:
raise ParseError(
f"No lattice information is present in {self.filename}")
# In case where b and c are not listed, we use the value of a
a, _ = get_number_with_esd(a_with_err)
b, _ = get_number_with_esd(block.get("_cell_length_b", a_with_err))
c, _ = get_number_with_esd(block.get("_cell_length_c", a_with_err))
alpha, _ = get_number_with_esd(block["_cell_angle_alpha"])
beta, _ = get_number_with_esd(block["_cell_angle_beta"])
gamma, _ = get_number_with_esd(block["_cell_angle_gamma"])
return a, b, c, alpha, beta, gamma
def lattice_parameters(self):
"""
Returns the lattice parameters associated to a CIF structure.
Returns
----------
a, b, c : float
Lengths of lattice vectors [Angstroms]
alpha, beta, gamma : float
Angles of lattice vectors [degrees].
"""
block = self.structure_block
try:
a, _ = get_number_with_esd(block["_cell_length_a"])
b, _ = get_number_with_esd(block["_cell_length_b"])
c, _ = get_number_with_esd(block["_cell_length_c"])
alpha, _ = get_number_with_esd(block["_cell_angle_alpha"])
beta, _ = get_number_with_esd(block["_cell_angle_beta"])
gamma, _ = get_number_with_esd(block["_cell_angle_gamma"])
except:
raise ParseError('Lattice vectors could not be determined.')
else:
return a, b, c, alpha, beta, gamma
def atoms(self):
"""
Asymmetric unit cell. Combine with CIFParser.symmetry_operators() for a full unit cell.
Returns
-------
atoms : iterable of Atom instance
"""
block = self.structure_block
try:
tmpdata = block.GetLoop("_atom_site_fract_x")
cartesian = False
except:
try:
tmpdata = block.GetLoop("_atom_site_Cartn_x")
cartesian = True
except:
raise ParseError(
"Atomic positions could not be found or inferred.")
t11 = block.get("_atom_sites_Cartn_tran_matrix_11")
t12 = block.get("_atom_sites_Cartn_tran_matrix_12")
t13 = block.get("_atom_sites_Cartn_tran_matrix_13")
t21 = block.get("_atom_sites_Cartn_tran_matrix_21")
t22 = block.get("_atom_sites_Cartn_tran_matrix_22")
t23 = block.get("_atom_sites_Cartn_tran_matrix_23")
t31 = block.get("_atom_sites_Cartn_tran_matrix_13")
t32 = block.get("_atom_sites_Cartn_tran_matrix_23")
t33 = block.get("_atom_sites_Cartn_tran_matrix_33")
cart_trans_matrix_inv = np.array([
[float(t11), float(t12), float(t13)],
[float(t21), float(t22), float(t23)],
[float(t31), float(t32), float(t33)],
])
cart_trans_matrix = inv(cart_trans_matrix_inv)
if not all([t11, t12, t13, t21, t22, t23, t31, t32, t33]):
raise ParseError(
"Cartesian coordinates in CIF but no transformation matrix given"
)
if cartesian:
xs = tmpdata.get("_atom_site_Cartn_x")
ys = tmpdata.get("_atom_site_Cartn_y")
zs = tmpdata.get("_atom_site_Cartn_z")
else:
xs = tmpdata.get("_atom_site_fract_x")
ys = tmpdata.get("_atom_site_fract_y")
zs = tmpdata.get("_atom_site_fract_z")
# TODO: handle wildcards like '?', '.' in xs, ys, zs
elements = tmpdata.get("_atom_site_type_symbol")
if not elements:
elements = tmpdata.get("_atom_site_label")
if not elements:
raise ParseError(
"Atom symbols could not be found or inferred.")
elements = map(lambda s: s.strip(punctuation + digits).title(),
elements)
atoms = list()
for e, x, y, z in zip(elements, xs, ys, zs):
coords = np.array([
get_number_with_esd(x)[0],
get_number_with_esd(y)[0],
get_number_with_esd(z)[0],
])
# We normalize atom position to be within the unit cell
# Therefore we need the fractional coordinates
if cartesian:
coords = transform(cart_trans_matrix, coords)
coords[:] = frac_coords(coords, self.lattice_vectors())
atoms.append(Atom(element=e, coords=np.mod(coords, 1)))
return atoms
