Electron poor materials research group
Group meeting Oct. 7, 2010
Theory- ZnSb, ZnAs, Mg3Sb2
and Li2Sb Equations of State
Procedure
• Binary search of minimum pressure 6-8 cycles
– each volume cycle contains 3 VASP runs
• 2 relaxation runs (back to back) and then a static run to
get accurate energy values
– 6-8 cycles take 30min-24hours
– each run is done in parallel on 3 cores.
– Only PAW_GGA was calculated as of now
• Values for the minimum volume V0, bulk modulus K0,
minimum energy E0, and derivative of the bulk modulus K0p
are then calculated from a 3rd order Birch-Murnaghan fit to
the volume and free energy points obtained from the Volume
cycles.
INCAR_relax
System = InSb
NSW = 5
| number of ionic steps
ISIF = 4
| ISIF=4 relax cellshape and ions. NOT volume
IBRION = 1 | ionic relaxation algorithm
EDIFF = 1E-4 | break condition for elec. SCF loop
EDIFFG = -1E-3 | break condition for ionic relaxation loop
MAXMIX = 80
NELMIN = 8
NFREE = 15
| keep dielectric function between ionic movements
| minimum number of electronic steps
| number of degrees of freedom (don't go above 20)
#RECOMMENDED MINIMUM SETUP
GGA=CA
#xchange-correlation
VOSKOWN=0
#=1 if GGA=91; else = 0
PREC = NORMAL
#PRECISION, sets fft grid
ENCUT = 150
#energy cutoff, commented to use enmax in potcar
LREAL = .FALSE.
#.FALSE. MEANS USE RECIPROCAL LATTICE
ISMEAR = 0
#0 means use gaussian smearing
INCAR_static
System = InSb
#ISTART = 0 # startjob: no WAVECAR file
#ICHARGE = 2 # charge: from atoms
#INIWAV = 1 # random initialization for wf.
NELM = 40
# maximum of 40 electronic steps
NELMIN = 2 # minimum of 2 steps
NELMDL = -5 # no update of charge for 3 steps
EDIFF = 1E-4 # accuracy for electronic minimization
#RECOMMENDED MINIMUM SETUP
GGA=CA
#xchange-correlation
VOSKOWN=0
#=1 if GGA=91; else = 0
PREC = NORMAL
#PRECISION, sets fft grid
ENCUT = 150
#energy cutoff, commented to use enmax in potcar
LREAL = .FALSE.
#.FALSE. MEANS USE RECIPROCAL LATTICE
ISMEAR = -5
#-5 means use tetrahedral with blochl
ZnSb
At Volume: 388.93 (experimental)
ALAT
=
B/A-ratio =
C/A-ratio =
6.202000000
1.248306998
1.306030313
At Volume: 402.53
Zn on site 8c (x,y,z): 0.4586, 0.1128, 0.8680
Sb on site 8c (x,y,z): 0.1420, 0.0812, 0.1077
According to BM minimum at: 403.65
LATTYP: Found a simple orthorhombic
cell.
ALAT
= 6.2818689569
Zn on site 8c (x,y,z): 0.4596, 0.1061, 0.8732
B/A-ratio = 1.2423943267
Sb on site 8c (x,y,z): 0.1416, 0.0831, 0.1096
C/A-ratio = 1.3070025754
ZnAs
At Volume: 312.38 (experimental)
ALAT
=
B/A-ratio =
C/A-ratio =
5.679000000
1.281387568
1.331044198
At Volume: 321.55
Zn on site 8c (x,y,z): 0.53, 0.614, 0.639
As on site 8c (x,y,z): 0.141, 0.076, 0.10
According to BM minimum at: 322.75
LATTYP: Found a simple orthorhombic
cell.
ALAT
= 5.7451115295
Zn on site 8c (x,y,z): 0.5387 0.6156 0.6338
B/A-ratio = 1.2739653477
As on site 8c (x,y,z): 0.1368 0.0743 0.1015
C/A-ratio = 1.3310458670
Mg3Sb2
At Volume: 130.64 (experimental)
ALAT
=
C/A-ratio =
4.568
1.582530648
Mg2 on site 2d (…z): 0.6339
Sb on site 2d (…z): 0.2283
At Volume: 133.13
LATTYP: Found a hexagonal cell.
ALAT
= 4.5958864285
C/A-ratio = 1.5836151843
According to BM minimum at: 133.09
Mg2 on site 2d (…z): 0.6324
Sb on site 2d (…z): 0.2261
Li2Sb
At Volume: 356.90 (experimental)
ALAT
=
C/A-ratio =
7.946
0.821419582
Li1 on site 6g (x…): 0.294
Li2 on site 6h (x,y,…): 0.622,0.010
Sb2 on site 4f (…z):0.0225
At Volume: 356.36
LATTYP: Found a hexagonal cell.
ALAT
= 7.9495656637
C/A-ratio = 0.8190784672
According to BM minimum at: 356.48
Li1 on site 6g (x…): 0.2926
Li2 on site 6h (x,y,…): 0.6318 0.0008
Sb2 on site 4f (…z):0.0017