[QE-users] Incorrect identification+generations of atoms in special positions (space_group options used).
Michal Husak
Michal.Husak at vscht.cz
Thu Nov 12 10:34:07 CET 2020
I had carefully checked this mailing list and I had found several
topic related to the same issue - QE generates multiple atoms for
atoms in special positions.
Not solved in any answer.
What I mean:
General position: x,y,z crystallographic position, atom not on a
symmetry element (e.g. for spac egropu number 11, P21/m , 4 atoms are
generated).
Special position: eg 2e x,z, (for space group 11, 2 atoms should be generated).
Atom is on the mirror element.
I had a structure described by CIF information in following way:
_symmetry_Int_Tables_number 11
_cell_length_a 6.1103(2)
_cell_length_b 20.6990(10)
_cell_length_c 11.7877(5)
_cell_angle_alpha 90.00
_cell_angle_beta 95.302(3)
_cell_angle_gamma 90.00
Zn 0.37830 0.2500 0.24657
The Zn is on the mirror
This can be transferred to QE input:
space_group = 11
uniqueb = .true.
A = 6.1103
B = 20.6990
C = 11.7877
cosAB = 0
cosAC = -0.092405345
cosBC = 0
And:
ATOMIC_POSITIONS crystal_sg
Zn 2e 0.37830 0.24657
Or
Zn 0.37830 0.2500 0.24657
Both input generate error = overlapped atoms.
What is wrong ?
Michal
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