spgrep
spgrep copied to clipboard
About the k-point used in the document example.
Here gives the following example:
from spgrep import get_spacegroup_irreps from spgrep.representation import get_character # Rutile structure (https://materialsproject.org/materials/mp-2657/) # P4_2/mnm (No. 136) a = 4.603 c = 2.969 x_4f = 0.3046 lattice = [ [a, 0, 0], [0, a, 0], [0, 0, c], ] positions = [ [0, 0, 0], # Ti(2a) [0.5, 0.5, 0.5], # Ti(2a) [x_4f, x_4f, 0], # O(4f) [-x_4f, -x_4f, 0], # O(4f) [-x_4f + 0.5, x_4f + 0.5, 0.5], # O(4f) [x_4f + 0.5, -x_4f + 0.5, 0.5], # O(4f) ] numbers = [0, 0, 1, 1, 1, 1] kpoint = [0.5, 0, 0] # X point irreps, rotations, translations, mapping_little_group = get_spacegroup_irreps( lattice, positions, numbers, kpoint ) # Symmetry operations by spglib assert len(rotations) == 16 assert len(translations) == 16 # At X point, the little co-group is isomorphic to mmm (order=8) assert len(mapping_little_group) == 8 print(mapping_little_group) # [ 0, 1, 4, 5, 8, 9, 12, 13] # Two two-dimensional irreps for irrep in irreps: print(get_character(irrep)) # [2.+0.j 0.+0.j 0.+0.j 2.+0.j 0.+0.j 0.+0.j 0.+0.j 0.+0.j] # [2.+0.j 0.+0.j 0.+0.j -2.+0.j 0.+0.j 0.+0.j 0.+0.j 0.+0.j]
In this example, the space group is P4_2/mnm (No. 136), and the selected k point is [0.5, 0, 0] (X point). I checked this information from BCS KVEC's convention represented here, as shown below:
As you can see, the two coordinates given above are not consistent. Any hints for this problem?
Regards, Zhao