Electron poor materials research group
Group meeting Dec 16, 2010
Theory- PAW_PBE psuedo
potentials. EOS relaxations and
bader analysis of resultant
structures.
System’s under study
 Electron Poor Materials




ZnSb
ZnAs
Li2Sb
Mg3Sb2
 Tetrahedral, sp3 systems






InSb
GaSb
ZnSe
ZnTe
GaAs
Si
Procedure
 Very accurate EOS relaxations were preformed.
 The system cell shape and volume was relaxed while the
volume was kept fixed to give a point in the EOS curve.
 A final relaxation was performed to bring the
system to the target volume given by the BirchMurnaghan EOS.
 From the final relaxation a static calculation was
performed to get the charge densities for Bader
analysis.
 Bader analysis was performed on the charge
densities from the static run.
Example INCAR for EOS relaxation.
It should be noted that not all relaxations have the same VASP setup
as I had difficulties with some of the systems crashing in VASP with
very accurate relaxation parameters. This was machine independent.
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-5 | break condition for elec. SCF loop
EDIFFG = -1E-4 | break condition for ionic relaxation loop
MAXMIX = 80
NELMIN = 6
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=
#xchange-correlation
#VOSKOWN=
#=1 if GGA=91; else = 0
PREC = ACCURATE
#PRECISION, sets fft grid
ENCUT = 225
#energy cutoff, commented to use enmax in potcar
LREAL = .FALSE.
#.FALSE. MEANS USE RECIPROCAL LATTICE
ISMEAR = 0
#0 means use gaussian smearing
Example INCAR for EOS static.
It should be noted that not all relaxations have the same VASP setup
as I had difficulties with some of the systems crashing in VASP with
very accurate relaxation parameters. This was machine independent.
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 = 4 # minimum of 2 steps
NELMDL = -5 # no update of charge for 3 steps
EDIFF = 1E-5 # accuracy for electronic minimization
#RECOMMENDED MINIMUM SETUP
#GGA=
#xchange-correlation
#VOSKOWN=
#=1 if GGA=91; else = 0
PREC = ACCURATE
#PRECISION, sets fft grid
ENCUT = 225
#energy cutoff, commented to use enmax in potcar
LREAL = .FALSE.
#.FALSE. MEANS USE RECIPROCAL LATTICE
ISMEAR = -5
#-5 means use tetrahedral with blochl
INCAR For final relaxation calculations
System = InSb relaxsetup.sh
NSW = 20
| number of ionic steps
ISIF = 4 | (ISIF=2 Relax ions only, ISIF=3 Relax everything)
IBRION = 1 | ionic relaxation algorithm
EDIFF = 1E-9 | break condition for elec. SCF loop
EDIFFG = -1E-8 | break condition for ionic relaxation loop
MAXMIX = 80
NELMIN = 8
NFREE = 20
| 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=
#xchange-correlation
#VOSKOWN=
#=1 if GGA=91; else = 0
PREC = ACCURATE
#PRECISION, sets fft grid
ENCUT = 225
#energy cutoff, determines number of lattice vectors
LREAL = .FALSE.
#.FALSE. MEANS USE RECIPROCAL LATTICE
ISMEAR = 0
#determines how partial occupancies a set.
INCAR For final static calculations
System = InSb
SIGMA = 0.01
#RECOMMENDED MINIMUM SETUP
PREC = ACCURATE
#PRECISION
ENCUT = 225
LREAL = .FALSE.
#.FALSE. MEANS USE
RECIPROCAL LATTICE
ISMEAR = 0
#USE GAUSSIAN SMEARING
#FOR GW CALCULATIONS
#LOPTICS = .TRUE.
#NBANDS = 96
#FOR BADER ANALYSIS
LAECHG=.TRUE.
NGXF = 126 #USE 6X NGX for bader analysis
NGYF = 126
NGZF = 126
Equations of State
The equations of state for the 10 materials are
below.
% differences are caluclated via:
Exp Vol: 67.97
PAW_PBE Vol: 73.48
Exp Vol: 56.63
PAW_PBE Vol: 60.31
Exp Vol: 45.98
PAW_PBE Vol: 47.35
Exp Vol: 56.83
PAW_PBE Vol: 59.17
Exp Vol: 45.17
lat constant: 5.6533
PAW_PBE Vol: 47.86
Exp Vol: 40.03
PAW_PBE Vol: 40.89
Exp Vol: 388.93
PAW_PBE Vol: 404.82
Exp Vol: 312.38
PAW_PBE Vol: 323.40
Exp Vol: 130.64
PAW_PBE Vol: 133.17
Exp Vol: 356.90
PAW_PBE Vol: 356.65
Li2Sb EOS troubles.
 The above graph is the ugliest out of the set which
makes me worry about the results for this structure.
 I have tried changing psuedo-potentials to include
more core electrons (currently there is only 1 valence
electron in the calculation).
 this however has crashed in the relaxation step I believe
due to the large number of plane waves needed. ENMAX in
POTCAR is 650 eV for Li_pv.
 It is not uncommon for VASP to in relaxation on
these larger systems if the plane waves gets too big
or the precision flag is set too high. This is machine
independent.
Equation of State Results.
Structure
Name
InSb
GaSb
ZnSe
ZnTe
GaAs
Si
ZnSb
ZnAs
Mg3Sb2
Li2Sb
Exp. Vol
(Ang^3)
67.97
56.63
45.98
56.83
45.17
40.03
388.93
312.38
130.64
356.90
VASP Vol
(Ang^3)
73.48
60.31
47.35
59.17
47.86
40.89
404.82
323.40
133.17
356.65
%diff
8.11
6.50
2.98
4.12
5.96
2.15
4.09
3.53
1.94
0.07
Bader analysis
bader analysis of the structures that were relaxed
from the target volume of the EOS calculations
above.
InSb
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000
2.6002
1.2908 29.8637
2
1.6622
1.6622
1.6622
5.3998
1.4395 43.6185
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
8.0000
Charge Transfer: 0.3998
GaSb
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000
2.7022
1.1483 22.2941
2
1.5563
1.5563
1.5563
5.2978
1.4227 38.0197
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
8.0000
Charge Transfer: 0.2978
ZnSe
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000 11.2714
1.0616 15.9986
2
1.4358
1.4358
1.4358
6.7286
1.3224 31.3555
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
18.0000
Charge Transfer: 0.7286
ZnTe
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000 11.4898
1.1104 18.5303
2
1.5464
1.5464
1.5464
6.5102
1.4456 40.6387
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
18.0000
Charge Transfer: 0.5102
GaAs
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000
2.3848
1.0766 18.1258
2
1.4409
1.4409
1.4409
5.6152
1.2941 29.7357
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
8.0000
Charge Transfer: 0.6152
Si
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000
3.9740
1.1403 20.3153
2
1.3672
1.3672
1.3672
4.0260
1.1183 20.5746
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
8.0000
Charge Transfer: 0.0260
ZnSb
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
2.8910
0.8296
7.1852 11.7353
1.1719 18.5852
2
0.2526
6.9946
3.0706 11.7353
1.1719 18.5852
3
3.3962
4.7417
5.1587 11.7353
1.1719 18.5852
4
6.0346
3.0825
1.0441 11.7353
1.1719 18.5852
5
3.3962
6.9946
1.0441 11.7353
1.1719 18.5852
6
6.0346
0.8296
5.1587 11.7353
1.1719 18.5852
7
2.8910
3.0825
3.0706 11.7353
1.1719 18.5852
8
0.2526
4.7417
7.1852 11.7353
1.1719 18.5852
9
0.8900
0.6496
0.9006
5.2645
1.3747 32.0161
10
2.2536
7.1746
5.0153
5.2650
1.3833 32.0181
11
5.3972
4.5617
3.2140
5.2650
1.3833 32.0181
12
4.0336
3.2625
7.3286
5.2645
1.3747 32.0161
13
5.3972
7.1746
7.3286
5.2650
1.3833 32.0181
14
4.0336
0.6496
3.2140
5.2645
1.3747 32.0161
15
0.8900
3.2625
5.0153
5.2645
1.3747 32.0161
16
2.2536
4.5617
0.9006
5.2650
1.3833 32.0181
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
136.0000
Charge Transfer: 0.2645
ZnAs
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
3.1025
4.5260
4.8534 11.5272
1.0976 15.9814
2
5.5241
2.8161
1.0239 11.5272
1.0976 15.9816
3
2.6485
0.8550
6.6352 11.5272
1.0976 15.9816
4
0.2270
6.4871
2.8056 11.5272
1.0976 15.9814
5
2.6485
2.8161
2.8056 11.5272
1.0976 15.9816
6
0.2270
4.5260
6.6352 11.5272
1.0976 15.9814
7
3.1025
6.4871
1.0239 11.5272
1.0976 15.9814
8
5.5241
0.8550
4.8534 11.5272
1.0976 15.9816
9
0.7864
0.5428
0.7776
5.4722
1.1688 24.4421
10
2.0891
6.7993
4.6072
5.4734
1.1816 24.4455
11
4.9647
4.2138
3.0519
5.4734
1.1816 24.4455
12
3.6619
3.1283
6.8814
5.4722
1.1688 24.4421
13
4.9647
6.7993
6.8814
5.4734
1.1816 24.4455
14
3.6619
0.5428
3.0519
5.4722
1.1688 24.4421
15
0.7864
3.1283
4.6072
5.4722
1.1688 24.4421
16
2.0891
4.2138
0.7776
5.4734
1.1816 24.4455
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
136.0000
Charge Transfer: 0.4722
Mg3Sb2
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
0.0000
0.0000
0.0000
0.5183
1.0492
8.8431
2
0.0000
2.6546
4.5981
0.5550
0.9734
8.5351
3
2.2989
1.3273
2.6757
0.5550
0.9734
8.5351
4
0.0000
2.6546
1.6400
7.1859
1.7652 53.6294
5
2.2989
1.3273
5.6338
7.1857
1.7652 53.6263
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
16.0000
Charge Transfer: 2.1859
Li2Sb
ACF.dat
#
X
Y
Z
CHARGE MIN DIST ATOMIC VOL
-------------------------------------------------------------------------------1
2.3289
0.0000
0.0000
0.1760
0.8271
4.1821
2
6.7906
2.0169
0.0000
0.1760
0.8271
4.1821
3
2.8130
4.8723
0.0000
0.1761
0.8331
4.1818
4
2.3289
0.0000
3.2538
0.1760
0.8271
4.1821
5
6.7906
2.0169
3.2538
0.1760
0.8271
4.1821
6
2.8130
4.8723
3.2538
0.1761
0.8331
4.1818
7
1.0465
6.8893
1.6269
0.1615
0.8513
4.2817
8 -2.5120
4.3509
1.6269
0.1615
0.8513
4.2817
9
1.4655
2.5383
1.6269
0.1616
0.8644
4.2829
10
5.4430
4.3509
4.8808
0.1615
0.8513
4.2817
11
5.0240
0.0000
4.8808
0.1615
0.8513
4.2817
12
1.4655
2.5383
4.8808
0.1616
0.8644
4.2829
13
0.0000
0.0000
1.6269
6.7396
1.5930 51.1225
14
0.0000
0.0000
4.8808
6.7396
1.5930 51.1225
15
0.0000
4.5928
6.5077
6.6271
1.5930 50.9728
16
0.0000
4.5928
3.2538
6.6271
1.5930 50.9728
17
3.9775
2.2964
0.0000
6.6206
1.5930 50.8370
18
3.9775
2.2964
3.2538
6.6206
1.5930 50.8370
-------------------------------------------------------------------------------VACUUM CHARGE:
0.0000
VACUUM VOLUME:
0.0000
NUMBER OF ELECTRONS:
42.0000
Charge Transfer: 1.7396
Bader Analysis results
Crystal
Name
Bader charge
transfer
Pauling
Electronegativity
Philips
Ionicity1
Si
ZnSb
GaSb
InSb
ZnAs
ZnTe
GaAs
ZnSe
Li2Sb
Mg3Sb2
0.026
0.2645
0.2978
0.3998
0.4722
0.5102
0.6152
0.7286
1.7396
2.1859
0
0.4
0.24
0.27
0.53
0.45
0.37
0.9
0
1.) Phillips. Rev. Mod. Phys. 42, 3, 1970
0.261
0.321
0.546
0.31
0.676