SYMMETRY_FIX

SYMMETRY_FIX allows you to constrain the symmetry of the displacements, vibrational amplitudes, and concentrations during LEED optimization.

Default: SYMMETRY_FIX = True: Use the symmetry determined automatically from the POSCAR file.

Syntax:

SYMMETRY_FIX = true
SYMMETRY_FIX = false
SYMMETRY_FIX = <group>

Accepted values: true, True, false, False or any combination of small/capital letters or any abbreviation of the words true and false (only the first character matters). Alternatively, <group> can be the Hermann–Mauguin symbol for the planar group you want to constrain your symmetry to. Acceptable values are listed in the table below.

Note

The program will evaluate the symmetry group of your input POSCAR, and will allow only symmetry reduction, i.e., the group you select must be a subgroup of the group of your input POSCAR. Take a look here for (i) a graphical representation of the operations in the group of your slab, (ii) a graphical representation of the diplacements allowed for each plane group, and (iii) a list of subgroups for each plane group. The symmetry group of your input slab is detected from the atomic coordinates in your input POSCAR (see also the parameter SYMMETRY_EPS), and written to the POSCAR header after initialization.

group	Special cases: reduction from some groups requires specification of which subgroup (see here)
p1	–
p2	–
pm	from pmm, p4m or rcmm specify either pm[1 0] or pm[0 1]
pg	from pgg, p4g or rcmm specify either pg[1 0] or pg[0 1]
cm	from p4m, p4g or rcmm specify either cm[1 1] or cm[1 -1]
	from p3m1 specify cm[1 -1], cm[2 1], or cm[1 2]
	from p31m specify cm[1 0], cm[0 1], or cm[1 1]
	from p6m specify cm[1 0], cm[0 1], cm[1 1], cm[1 -1], cm[1 2], or cm[2 1]
rcm	Note: not a real plane group, see here (cm with non-primitive cell. Calculation times will be longer than with the primitive cell!)
	from rcmm specify either rcm[1 0] or rcm[0 1]
pmm	–
pmg	from rcmm specify either pmg[1 0] or pmg[0 1]
pgg	–
cmm	from p6m specify cmm[1 2] (or cmm[1 0]), cmm[2 1] (or cmm[0 1]), cmm[1 -1] (or cmm[1 1]). Alternatives in parentheses are equivalent
rcmm	Note: not a real plane group, see here (cmm with non-primitive cell. Calculation times will be longer than with the primitive cell!)
p4	–
p4m	–
p4g	–
p3	–
p3m1	–
p31m	–
p6	–
p6m	–