Electron poor materials research group

Group meeting Nov 11, 2010

Theory- Bader Analysis -> FCC

Procedure• Static Calculations of the 4 FCC structures were computed

– Calculations were done on a Gamma 9X9X9 grid– An extra flag was used in the INCAR file: LAECHG = .TRUE.

• Turns on All Electron CHGCAR file outputs and outputs 3 files• AECCAR0: core charge density• AECCAR1: atomic AE charge density (overlapping atomic charge density)• AECCAR2: AE charge density

• The files AECCAR0 and AECCAR2 are added together for bader analysis per instructions: http://theory.cm.utexas.edu/bader/vasp.php– chgsum.sh AECCAR0 AECCAR2, chsum is a shellscript

• Outputs CHGCAR_sum

• Bader analysis is done on the vasp CHGCAR from the static run– bader.x -p atom_index -p bader_index CHGCAR -ref CHGCAR_sum

• atom_index: Write the atomic volume index to a charge density file• bader_index: Write the Bader volume index to a charge density file

NOTES• Only the PAW potentials can output there core charges for bader

analysis• A fine fft grid is needed to accurately reproduce the correct total

core charge. It is essential to do a few calculations, increasing NG(X,Y,Z)F until the total charge is correct.

• The outputs from bader.x are:– ACF.dat – Atomic Coordinate file. Shows the location and charge of the

atoms– BCF.dat – Bader Coordinate file.– AVF.dat – Atomic Volume file. Used to keep track of other files that may

be output with the bader program with flag –p all_atom– AtIndex.dat (only with –p atom_index) – charge density file which

contains the atomic borders– BvIndex.dat (only with –p bader_index) –charge density file which

contains the bader borders

INCAR_staticSystem = GaAs

SIGMA = 0.01

#RECOMMENDED MINIMUM SETUPPREC = NORMAL #PRECISIONENCUT = 275#LREAL = .FALSE. #.FALSE. MEANS USE RECIPROCAL LATTICEISMEAR = 0 #USE GAUSSIAN SMEARING

LAECHG=.TRUE.

Electronegativity (EN)using Pauling Scale

GaAs # X Y Z CHARGE MIN DIST ATOMIC VOL -------------------------------------------------------------------------------- 1 0.0000 0.0000 0.0000 2.2907 0.8192 16.8049 2 1.4133 1.4133 1.4133 5.7093 1.0377 28.3647 -------------------------------------------------------------------------------- VACUUM CHARGE: 0.0000 VACUUM VOLUME: 0.0000 NUMBER OF ELECTRONS: 8.0000

ACF.dat :

ENAs – ENGa = 0.37 Bader charge shift = 0.7093

GaAs Bader Volume Bounding Boxes

All other FCC bounding boxes look virtually identical to this one

InSb# X Y Z CHARGE MIN DIST ATOMIC VOL -------------------------------------------------------------------------------- 1 0.0000 0.0000 0.0000 2.7177 1.1221 28.7015 2 1.6196 1.6196 1.6196 5.2823 1.2174 39.2663 -------------------------------------------------------------------------------- VACUUM CHARGE: 0.0000 VACUUM VOLUME: 0.0000 NUMBER OF ELECTRONS: 8.0000

ACF.dat :

ENSb – ENIn = 0.27 Bader charge shift = 0.2823

GaSb# X Y Z CHARGE MIN DIST ATOMIC VOL -------------------------------------------------------------------------------- 1 0.0000 0.0000 0.0000 2.8499 0.9801 22.0766 2 1.5240 1.5240 1.5240 5.1501 1.1732 34.5544 -------------------------------------------------------------------------------- VACUUM CHARGE: 0.0000 VACUUM VOLUME: 0.0000 NUMBER OF ELECTRONS: 8.0000

ACF.dat :

ENSb – ENGa = 0.24 Bader charge shift = 0.1501

ZnSe# X Y Z CHARGE MIN DIST ATOMIC VOL -------------------------------------------------------------------------------- 1 0.0000 0.0000 0.0000 11.3512 0.9048 16.2281 2 1.4218 1.4218 1.4218 6.6488 1.1507 29.7541 -------------------------------------------------------------------------------- VACUUM CHARGE: 0.0000 VACUUM VOLUME: 0.0000 NUMBER OF ELECTRONS: 18.0000

ACF.dat :

ENSe – ENZn = 0.9 Bader charge shift = 0.6488

ZnTe # X Y Z CHARGE MIN DIST ATOMIC VOL -------------------------------------------------------------------------------- 1 0.0000 0.0000 0.0000 11.5271 0.8809 18.6275 2 1.5258 1.5258 1.5258 6.4729 1.2743 38.2015 -------------------------------------------------------------------------------- VACUUM CHARGE: 0.0000 VACUUM VOLUME: 0.0000 NUMBER OF ELECTRONS: 18.0000

ACF.dat :

ENTe – ENZn = 0.45 Bader charge shift = 0.4729

FCC Comparisons

Compound Name EN2-EN1 Bader

GaSb 0.24 0.1501

InSb 0.27 0.2823

GaAs 0.37 0.7093

ZnTe 0.45 0.4729

ZnSe 0.9 0.6488