electron poor materials research group
DESCRIPTION
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 Li 2 Sb Mg 3 Sb 2 Tetrahedral, sp 3 systems InSb GaSb ZnSe ZnTe - PowerPoint PPT PresentationTRANSCRIPT
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 Birch-Murnaghan 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.
System = InSb
NSW = 5 | number of ionic stepsISIF = 4 | ISIF=4 relax cellshape and ions. NOT volumeIBRION = 1 | ionic relaxation algorithmEDIFF = 1E-5 | break condition for elec. SCF loopEDIFFG = -1E-4 | break condition for ionic relaxation loop
MAXMIX = 80 | keep dielectric function between ionic movementsNELMIN = 6 | minimum number of electronic stepsNFREE = 15 | number of degrees of freedom (don't go above 20)
#RECOMMENDED MINIMUM SETUP#GGA= #xchange-correlation#VOSKOWN= #=1 if GGA=91; else = 0PREC = ACCURATE #PRECISION, sets fft gridENCUT = 225 #energy cutoff, commented to use enmax in potcarLREAL = .FALSE. #.FALSE. MEANS USE RECIPROCAL LATTICEISMEAR = 0 #0 means use gaussian smearing
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.
Example INCAR for EOS 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 stepsNELMIN = 4 # minimum of 2 stepsNELMDL = -5 # no update of charge for 3 stepsEDIFF = 1E-5 # accuracy for electronic minimization
#RECOMMENDED MINIMUM SETUP#GGA= #xchange-correlation#VOSKOWN= #=1 if GGA=91; else = 0PREC = ACCURATE #PRECISION, sets fft gridENCUT = 225 #energy cutoff, commented to use enmax in potcarLREAL = .FALSE. #.FALSE. MEANS USE RECIPROCAL LATTICEISMEAR = -5 #-5 means use tetrahedral with blochl
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.
INCAR For final relaxation calculations
System = InSb relaxsetup.sh
NSW = 20 | number of ionic stepsISIF = 4 | (ISIF=2 Relax ions only, ISIF=3 Relax everything)IBRION = 1 | ionic relaxation algorithmEDIFF = 1E-9 | break condition for elec. SCF loopEDIFFG = -1E-8 | break condition for ionic relaxation loop
MAXMIX = 80 | keep dielectric function between ionic movementsNELMIN = 8 | minimum number of electronic stepsNFREE = 20 | number of degrees of freedom (don't go above 20)
#RECOMMENDED MINIMUM SETUP#GGA= #xchange-correlation#VOSKOWN= #=1 if GGA=91; else = 0PREC = ACCURATE #PRECISION, sets fft gridENCUT = 225 #energy cutoff, determines number of lattice vectorsLREAL = .FALSE. #.FALSE. MEANS USE RECIPROCAL LATTICEISMEAR = 0 #determines how partial occupancies a set.
INCAR For final static calculations
System = InSb
SIGMA = 0.01
#RECOMMENDED MINIMUM SETUPPREC = ACCURATE #PRECISIONENCUT = 225 LREAL = .FALSE. #.FALSE. MEANS USE RECIPROCAL LATTICEISMEAR = 0 #USE GAUSSIAN SMEARING
#FOR GW CALCULATIONS#LOPTICS = .TRUE.#NBANDS = 96
#FOR BADER ANALYSISLAECHG=.TRUE.NGXF = 126 #USE 6X NGX for bader analysisNGYF = 126NGZF = 126
The equations of state for the 10 materials are below.
Equations of State
% 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
PAW_PBE Vol: 47.86
lat constant: 5.6533
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
Exp. Vol (Ang^3)
VASP Vol (Ang^3) %diff
InSb 67.97 73.48 8.11GaSb 56.63 60.31 6.50ZnSe 45.98 47.35 2.98ZnTe 56.83 59.17 4.12GaAs 45.17 47.86 5.96Si 40.03 40.89 2.15ZnSb 388.93 404.82 4.09ZnAs 312.38 323.40 3.53Mg3Sb2 130.64 133.17 1.94Li2Sb 356.90 356.65 0.07
bader analysis of the structures that were relaxed from the target volume of the EOS calculations above.
Bader analysis
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 0.026 0 0ZnSb 0.2645 0.4GaSb 0.2978 0.24 0.261InSb 0.3998 0.27 0.321ZnAs 0.4722 0.53ZnTe 0.5102 0.45 0.546GaAs 0.6152 0.37 0.31ZnSe 0.7286 0.9 0.676Li2Sb 1.7396Mg3Sb2 2.1859
1.) Phillips. Rev. Mod. Phys. 42, 3, 1970