Exchange of atoms...

[danith]

Hi VASP users,

Im triying to do a exchange of Sb for As on a cell of GaSb, the problem is that I dont know how to do it... Could anyone help me?

Thank you very much in advance....

POSCAR

Ga32 Sb32 As (P1) ~ GaSbAs2x2x2 (VASP)
1.0
21.76470000 0.00000000 0.00000000
0.00000000 21.33400000 0.00000000
0.00000000 0.00000000 21.71476000
32 32 1
Direct
0.50000000 0.50000000 0.50000000
0.50000000 0.64285647 0.64035154
0.64002950 0.50000000 0.64035154
0.64002950 0.64285647 0.50000000
0.64002950 0.64285647 0.78070308
0.64002950 0.78571295 0.64035154
0.50000000 0.78571295 0.78070308
0.78005899 0.64285647 0.64035154
0.78005899 0.50000000 0.78070308
0.78005899 0.78571295 0.50000000
0.50000000 0.50000000 0.78070308
0.50000000 0.64285647 0.92105462
0.64002950 0.50000000 0.92105462
0.64002950 0.78571295 0.92105462
0.78005899 0.64285647 0.92105462
0.78005899 0.78571295 0.78070308
0.50000000 0.78571295 0.50000000
0.50000000 0.92856942 0.64035154
0.64002950 0.92856942 0.50000000
0.64002950 0.92856942 0.78070308
0.78005899 0.92856942 0.64035154
0.50000000 0.92856942 0.92105462
0.78005899 0.92856942 0.92105462
0.78005899 0.50000000 0.50000000
0.92008849 0.50000000 0.64035154
0.92008849 0.64285647 0.50000000
0.92008849 0.64285647 0.78070308
0.92008849 0.78571295 0.64035154
0.92008849 0.50000000 0.92105462
0.92008849 0.78571295 0.92105462
0.92008849 0.92856942 0.50000000
0.92008849 0.92856942 0.78070308
0.57001245 0.57142589 0.57017347
0.57001245 0.71428237 0.71052501
0.71004195 0.57142589 0.71052501
0.71004195 0.71428237 0.57017347
0.57001245 0.57142589 0.85087655
0.57001245 0.71428237 0.99123269
0.71004195 0.57142589 0.99123269
0.71004195 0.71428237 0.85087655
0.57001245 0.85713884 0.57017347
0.57001245 0.00000000 0.71052501
0.71004195 0.85713884 0.71052501
0.71004195 0.00000000 0.57017347
0.57001245 0.85713884 0.85087655
0.57001245 0.00000000 0.99123269
0.71004195 0.85713884 0.99123269
0.71004195 0.00000000 0.85087655
0.85007145 0.57142589 0.57017347
0.85007145 0.71428237 0.71052501
0.99010554 0.57142589 0.71052501
0.99010554 0.71428237 0.57017347
0.85007145 0.57142589 0.85087655
0.85007145 0.71428237 0.99123269
0.99010554 0.57142589 0.99123269
0.99010554 0.71428237 0.85087655
0.85007145 0.85713884 0.57017347
0.85007145 0.00000000 0.71052501
0.99010554 0.85713884 0.71052501
0.99010554 0.00000000 0.57017347
0.85007145 0.85713884 0.85087655
0.85007145 0.00000000 0.99123269
0.99010554 0.85713884 0.99123269
0.99010554 0.00000000 0.85087655
0.00000000 0.70270601 0.00000000

KPOINTS
Automatic mesh
0
Monkhorst Pack
1 1 1
0. 0. 0.

INCAR

# SCF input for VASP
# Note that VASP uses the FIRST occurence of a keyword
SYSTEM = Ga32 Sb32 As (P1) ~ GaSbAs2x2x2 (VASP)

PREC = Normal
ENCUT = 282.697
IBRION = 2
NSW = 100
ISIF = 2
ALGO = Normal (blocked Davidson)
NELM = 60
NELMIN = 2
EDIFF = 1.0e-05
EDIFFG = -0.02
VOSKOWN = 1
NBLOCK = 1
ISPIN = 1
INIWAV = 1
ISTART = 0
ICHARG = 2
LWAVE = .FALSE.
LCHARG = .TRUE.
ADDGRID = .FALSE.
ISMEAR = 1
SIGMA = 0.2
LREAL = .FALSE.
RWIGS = 1.26 1.40 1.2

[Danny]

instead of using a POTCAR file with Ga and Sb use a POTCAR file with Ga and As...i.e. just make a new POTCAR like
cat POTCAR_Ga POTCAR_As >> POTACR_GaAs
(and rename to POTCAR for the clculation of course

Danny