Sb on Surface....

[danith]

Hello Everyone and VASP users,

Im trying to do a calculation of Sb on Surface of GaSb, but I don't know what happen. My first step was optimize the GaSb surface to find the KPOINTS and ECUT. Right now I've creating a supercell 2x2x2, and put in the Sb metal onto GaSb surface, but when I trying run the calculation is wrong.... Could someone help?

INCAR:

# SCF input for VASP
# Note that VASP uses the FIRST occurence of a keyword
SYSTEM = (Ga Sb)4 (F-43m) ~ Gallium antimonide (ICSD #635307)_3 (VASP)

PREC = High
ENCUT = 520
IBRION = 2
NSW = 100
ISIF = 3
ALGO = Normal (blocked Davidson)
NELM = 60
NELMIN = 2
EDIFF = 1.0e-06
EDIFFG = -0.02
VOSKOWN = 1
NBLOCK = 1
ISPIN = 1
INIWAV = 1
ISTART = 0
ICHARG = 2
LWAVE = .FALSE.
LCHARG = .FALSE.
ADDGRID = .FALSE.
ISMEAR = 1
SIGMA = 0.2
LREAL = Auto
RWIGS = 1.26 1.40

KPOINTS:

Automatic mesh
0
Monkhorst Pack
15 15 15
0. 0. 0.

POSCAR:

CIF file
1.0
13.9636001587 0.0000000000 0.0000000000
0.0000000000 30.1040000916 0.0000000000
0.0000000000 0.0000000000 13.2489004135
27 10
Direct
0.248500004 0.806999981 0.508099973
0.266000003 0.554199994 0.838400006
0.262400001 0.554700017 0.175600007
0.279900014 0.301899999 0.505900025
0.772400022 0.645399988 0.504400015
0.789799988 0.392699987 0.834599972
0.786099970 0.393200010 0.171800002
0.803600013 0.140300006 0.502099991
0.510500014 0.726199985 0.506200016
0.527899981 0.473399997 0.836600006
0.524299979 0.473899990 0.173700005
0.541700006 0.221100003 0.504000008
0.255499989 0.680800021 0.341800004
0.272899985 0.428000003 0.672200024
0.779299974 0.519299984 0.338000000
0.796800017 0.266499996 0.668399990
0.517300010 0.600099981 0.340000004
0.534799993 0.347200006 0.670400023
0.257400006 0.680599988 0.673300028
0.271100014 0.428299993 0.340799987
0.781099975 0.519100010 0.669399977
0.794900000 0.266799986 0.336899996
0.519200027 0.599799991 0.671400011
0.532999992 0.347600013 0.338800013
0.264200002 0.554400027 0.507000029
0.787899971 0.392899990 0.503199995
0.526099980 0.473600000 0.505100012
0.317999989 0.723599970 0.507399976
0.579800010 0.642899990 0.505500019
0.324900001 0.597500026 0.340999991
0.586799979 0.516700029 0.339100003
0.326700002 0.597199976 0.672599971
0.588599980 0.516499996 0.670599997
0.333499998 0.471100003 0.506200016
0.595499992 0.390300006 0.504400015
0.504400015 0.655099988 0.256900012
0.136899993 0.599699974 0.558200002

Thank you in advance,

Danith

[alex]

Hi Danith,

some general hints:
- try to get along with as low as possible INCAR settings
- use Prec = Accu (High is outdated)
- read about RWIGS. Do you really need to fix that?
VASP uses a lot of standard settings and will work fine with them! Read the manual about your settings. Never usr inheritated INCARs without checking.

about KPOINTS:
- if you calc. a slab, 1 k-point in this direction is enough (no periodicty though)
- is GaSb semiconducting? I'd guess you'll be fine with far less k-points, esp. you have a huge supercell. Try to break down the number of k-points from a bulk calculation (e.g. 4x4x4) according to the size of the unit. E.g. you have a bulk and need a 4x4x4 set (for say 5x5x5 A^3) and you end up with a 10x10x30 surface slab, go to 2x2x1.

Cheers,

alex

PS: nobody can tell from the input what goes wrong. You need to be more detailed about that.

[danith]

Hey Alex thank you very much, you are right... Im trying right now....