[Pw_forum] Band Offsets too large

Dae Kwang Jun jdaekwang at gmail.com
Wed Jun 29 07:25:16 CEST 2016


Dear all,

I tried to calculate the band offset for GaAs-AlAs. However, the valence
band offsets that I am getting are too large. I used 6 unit cells of GaAs
and 6 unit cells of AlAs stacked in the 001 direction. For the offset I
used the potential line up method. I used pw.x pp.x average.x to find the
potential line up, and I used pw.x bands.x plotband.x to find the valence
band maxima. Most literature agrees that the VBO should be around 0.44 eV
to 0.50 eV. However, I am getting 2.49 eV, which is too large. What could
be causing this?

Sincerely,

Dae Kwang Jun

Here is one of the input files that I used for the GaAs-AlAs interface

&CONTROL
calculation = 'scf'
verbosity = 'high'
restart_mode = 'from_scratch'
tstress = .true.
tprnfor = .true.
outdir = '/home/files'
prefix = '001_5x5_GaAs-AlAs'
pseudo_dir = '/home/espresso-5.4.0/pseudo'
/
&SYSTEM
ibrav = 6
a = 5.65
c = 67.8
nat = 96
ntyp = 3
ecutwfc = 70.0
occupations = 'smearing'
degauss = 0.01
/
&ELECTRONS
mixing_beta = 0.4
diagonalization = 'david'
/
ATOMIC_SPECIES
Ga    69.723    Ga.pw-mt_fhi.UPF
Al    26.981    Al.pw-mt_fhi.UPF
As    74.921    As.pw-mt_fhi.UPF
ATOMIC_POSITIONS {angstrom}
Ga     0.000000     0.000000     0.000000
Ga     0.000000     2.825000     2.825000
Ga     2.825000     0.000000     2.825000
Ga     2.825000     2.825000     0.000000
As     1.412500     1.412500     1.412500
As     4.237500     4.237500     1.412500
As     4.237500     1.412500     4.237500
As     1.412500     4.237500     4.237500
Al     0.000000     0.000000     33.900002
Al     0.000000     2.825000     36.725002
Al     2.825000     0.000000     36.725002
Al     2.825000     2.825000     33.900002
As     1.412500     1.412500     35.312500
As     4.237500     4.237500     35.312500
As     4.237500     1.412500     38.137501
As     1.412500     4.237500     38.137501
Ga     0.000000     0.000000     5.650000
Ga     0.000000     2.825000     8.475000
Ga     2.825000     0.000000     8.475000
Ga     2.825000     2.825000     5.650000
As     1.412500     1.412500     7.062500
As     4.237500     4.237500     7.062500
As     4.237500     1.412500     9.887501
As     1.412500     4.237500     9.887501
Ga     0.000000     0.000000     11.300000
Ga     0.000000     2.825000     14.125000
Ga     2.825000     0.000000     14.125000
Ga     2.825000     2.825000     11.300000
As     1.412500     1.412500     12.712501
As     4.237500     4.237500     12.712501
As     4.237500     1.412500     15.537500
As     1.412500     4.237500     15.537500
Ga     0.000000     0.000000     16.950001
Ga     0.000000     2.825000     19.775002
Ga     2.825000     0.000000     19.775002
Ga     2.825000     2.825000     16.950001
As     1.412500     1.412500     18.362501
As     4.237500     4.237500     18.362501
As     4.237500     1.412500     21.187500
As     1.412500     4.237500     21.187500
Ga     0.000000     0.000000     22.600000
Ga     0.000000     2.825000     25.425001
Ga     2.825000     0.000000     25.425001
Ga     2.825000     2.825000     22.600000
As     1.412500     1.412500     24.012501
As     4.237500     4.237500     24.012501
As     4.237500     1.412500     26.837502
As     1.412500     4.237500     26.837502
Ga     0.000000     0.000000     28.250000
Ga     0.000000     2.825000     31.075001
Ga     2.825000     0.000000     31.075001
Ga     2.825000     2.825000     28.250000
As     1.412500     1.412500     29.662500
As     4.237500     4.237500     29.662500
As     4.237500     1.412500     32.487499
As     1.412500     4.237500     32.487499
Al     0.000000     0.000000     39.549999
Al     0.000000     2.825000     42.375000
Al     2.825000     0.000000     42.375000
Al     2.825000     2.825000     39.549999
As     1.412500     1.412500     40.962498
As     4.237500     4.237500     40.962498
As     4.237500     1.412500     43.787498
As     1.412500     4.237500     43.787498
Al     0.000000     0.000000     45.200001
Al     0.000000     2.825000     48.025002
Al     2.825000     0.000000     48.025002
Al     2.825000     2.825000     45.200001
As     1.412500     1.412500     46.612499
As     4.237500     4.237500     46.612499
As     4.237500     1.412500     49.437500
As     1.412500     4.237500     49.437500
Al     0.000000     0.000000     50.850002
Al     0.000000     2.825000     53.675003
Al     2.825000     0.000000     53.675003
Al     2.825000     2.825000     50.850002
As     1.412500     1.412500     52.262501
As     4.237500     4.237500     52.262501
As     4.237500     1.412500     55.087502
As     1.412500     4.237500     55.087502
Al     0.000000     0.000000     56.500000
Al     0.000000     2.825000     59.325001
Al     2.825000     0.000000     59.325001
Al     2.825000     2.825000     56.500000
As     1.412500     1.412500     57.912498
As     4.237500     4.237500     57.912498
As     4.237500     1.412500     60.737499
As     1.412500     4.237500     60.737499
Al     0.000000     0.000000     62.150002
Al     0.000000     2.825000     64.974998
Al     2.825000     0.000000     64.974998
Al     2.825000     2.825000     62.150002
As     1.412500     1.412500     63.562500
As     4.237500     4.237500     63.562500
As     4.237500     1.412500     66.387505
As     1.412500     4.237500     66.387505
K_POINTS {automatic}
8 8 2 0 0 0
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