[Pw_forum] Transmission calculation for simple metals
Vladislav Borisov
vladislav.borisov at physik.uni-halle.de
Fri Jul 18 10:39:23 CEST 2014
Dear all,
I have a general question about calculating the transmission function
for simple metals. On the example of ferromagnetic fcc cobalt, I performed
a spin-polarized calculation of transmission using the latest version
of PWCOND (v.5.1). Below are the input data for this system.
Input for the self-consistent calculation:
&control
calculation='scf',
restart_mode='from_scratch',
pseudo_dir = '/scratch/vborisov/pseudo/',
outdir='/scratch/vborisov/tmp/Co-Transmission/',
prefix='fct-2',
wf_collect=.true.
/
&system
ibrav = 6,
celldm(1) = 7.35477531275,
celldm(3) = 0.756973279,
nat = 4,
ntyp = 1,
nspin = 2,
nbnd = 40,
starting_magnetization(1)=+1.80,
ecutwfc = 63.0,
ecutrho = 504.0,
occupations='smearing',
smearing='methfessel-paxton',
degauss=0.02
/
&electrons
conv_thr = 1.0e-8
mixing_beta = 0.25
/
ATOMIC_SPECIES
Co 58.933 Co.pbe-nd-rrkjus.UPF
ATOMIC_POSITIONS {crystal}
Co 0.00 0.00 0.25
Co 0.50 0.50 0.25
Co 0.00 0.50 0.75
Co 0.50 0.00 0.75
K_POINTS {automatic}
15 15 20 0 0 0
One of the inputs for the transmission calculation:
&inputcond
outdir = '/scratch/vborisov/tmp/Co-Transmission',
prefixl = 'fct-2',
prefixs = 'fct-2',
tran_file = 'TJ-k1550.Ef'
ikind = 1,
iofspin = 2,
energy0 = 0.00d0,
denergy = -0.01d0,
ewind = 2.d0,
epsproj = 1.d-5,
delgep = 1.d-7,
cutplot = 3.d0,
nz1 = 22
/
1
0.00510204 0.13775510 1
1
At the end of the output file, one finds the following data:
ngper, shell number = 271 271
ngper, n2d = 271 121
--- E-Ef = 0.0000000 k = 0.0051020 0.1377551
--- ie = 1 ik = 1
Nchannels of the left tip = 30
Right moving states:
k1(2pi/a) k2(2pi/a) E-Ef (eV)
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 0.0000000 0.0000000
-0.0964682 -0.0000000 0.0000000
-0.0964689 -0.0000000 0.0000000
-0.0964705 0.0000000 0.0000000
-0.0964798 -0.0000000 0.0000000
-0.0965107 0.0000000 0.0000000
-0.0965482 0.0000000 0.0000000
-0.0966171 0.0000000 0.0000000
-0.0968639 0.0000000 0.0000000
-0.0985616 0.0000000 0.0000000
-0.1341194 0.0000003 0.0000000
-0.1855624 0.0000002 0.0000000
-0.2949790 0.0000002 0.0000000
-0.3297361 0.0000000 0.0000000
0.4517894 -0.0000001 0.0000000
Left moving states:
k1(2pi/a) k2(2pi/a) E-Ef (eV)
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964682 -0.0000000 0.0000000
0.0964689 0.0000000 0.0000000
0.0964705 0.0000000 0.0000000
0.0964798 -0.0000000 0.0000000
0.0965107 0.0000000 0.0000000
0.0965482 0.0000000 0.0000000
0.0966171 0.0000000 0.0000000
0.0968639 0.0000000 0.0000000
0.0985616 0.0000000 0.0000000
0.1341194 0.0000003 0.0000000
0.1855624 0.0000002 0.0000000
0.2949790 0.0000002 0.0000000
0.3297361 0.0000000 0.0000000
-0.4517894 -0.0000001 0.0000000
to transmit
Band j to band i transmissions and reflections:
j i |T_ij|^2 |R_ij|^2
1 --> 1 1.00000 0.00000
1 --> 2 0.00000 0.00000
1 --> 3 0.00000 0.00000
1 --> 4 0.00000 0.00000
1 --> 5 0.00000 0.00000
1 --> 6 0.00000 0.00000
1 --> 7 0.00000 0.00000
1 --> 8 0.00000 0.00000
1 --> 9 0.00000 0.00000
1 --> 10 0.00000 0.00000
1 --> 11 0.00000 0.00000
1 --> 12 0.00000 0.00000
1 --> 13 0.00000 0.00000
1 --> 14 0.00000 0.00000
1 --> 15 0.00000 0.00000
1 --> 16 0.00000 0.00000
1 --> 17 0.00000 0.00000
1 --> 18 0.00000 0.00000
1 --> 19 0.00000 0.00000
1 --> 20 0.00000 0.00000
1 --> 21 0.00000 0.00000
1 --> 22 0.00000 0.00000
1 --> 23 0.00000 0.00000
1 --> 24 0.00000 0.00000
1 --> 25 0.00000 0.00000
1 --> 26 0.00000 0.00000
1 --> 27 0.00000 0.00000
1 --> 28 0.00000 0.00000
1 --> 29 0.00000 0.00000
1 --> 30 0.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
2 --> 1 0.00000 0.00000
2 --> 2 1.00000 0.00000
2 --> 3 0.00000 0.00000
2 --> 4 0.00000 0.00000
2 --> 5 0.00000 0.00000
2 --> 6 0.00000 0.00000
2 --> 7 0.00000 0.00000
2 --> 8 0.00000 0.00000
2 --> 9 0.00000 0.00000
2 --> 10 0.00000 0.00000
2 --> 11 0.00000 0.00000
... (the same for all other channels)
30 --> 24 0.00000 0.00000
30 --> 25 0.00000 0.00000
30 --> 26 0.00000 0.00000
30 --> 27 0.00000 0.00000
30 --> 28 0.00000 0.00000
30 --> 29 0.00000 0.00000
30 --> 30 1.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
E-Ef(ev), T = 0.0000000 30.0000000
T_tot 0.00000 0.30000E+02
PWCOND : 1m25.79s CPU 3m 6.30s WALL
init : 33.04s CPU 133.41s WALL ( 1 calls)
poten : 0.02s CPU 0.02s WALL ( 2 calls)
local : 2.43s CPU 2.46s WALL ( 1 calls)
scatter_forw : 49.34s CPU 49.42s WALL ( 2 calls)
compbs : 0.83s CPU 0.84s WALL ( 1 calls)
compbs_2 : 0.62s CPU 0.63s WALL ( 1 calls)
The transmission is way too large for this material, so the result is obviously wrong.
However, if I set the epsproj parameter to a larger value, e.g. 10^-4, then I get the
correct result T=4 (see below):
ngper, shell number = 271 271
ngper, n2d = 271 69
--- E-Ef = 0.0000000 k = 0.0051020 0.1377551
--- ie = 1 ik = 1
Nchannels of the left tip = 4
Right moving states:
k1(2pi/a) k2(2pi/a) E-Ef (eV)
-0.1543659 0.0000003 0.0000000
-0.1880694 0.0000001 0.0000000
-0.2967059 0.0000002 0.0000000
0.4430621 -0.0000001 0.0000000
Left moving states:
k1(2pi/a) k2(2pi/a) E-Ef (eV)
0.1543659 0.0000003 0.0000000
0.1880695 0.0000002 0.0000000
0.2967060 0.0000002 0.0000000
-0.4430621 -0.0000001 0.0000000
to transmit
Band j to band i transmissions and reflections:
j i |T_ij|^2 |R_ij|^2
1 --> 1 1.00000 0.00000
1 --> 2 0.00000 0.00000
1 --> 3 0.00000 0.00000
1 --> 4 0.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
2 --> 1 0.00000 0.00000
2 --> 2 1.00000 0.00000
2 --> 3 0.00000 0.00000
2 --> 4 0.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
3 --> 1 0.00000 0.00000
3 --> 2 0.00000 0.00000
3 --> 3 1.00000 0.00000
3 --> 4 0.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
4 --> 1 0.00000 0.00000
4 --> 2 0.00000 0.00000
4 --> 3 0.00000 0.00000
4 --> 4 1.00000 0.00000
Total T_j, R_j = 1.00000 0.00000
E-Ef(ev), T = 0.0000000 4.0000000
T_tot 0.00000 0.40000E+01
PWCOND : 1m14.44s CPU 2m14.19s WALL
init : 33.20s CPU 92.90s WALL ( 1 calls)
poten : 0.02s CPU 0.02s WALL ( 2 calls)
local : 1.86s CPU 1.88s WALL ( 1 calls)
scatter_forw : 38.94s CPU 38.96s WALL ( 2 calls)
compbs : 0.37s CPU 0.39s WALL ( 1 calls)
compbs_2 : 0.29s CPU 0.30s WALL ( 1 calls)
This situation is observed quite seldom (a few points in the BZ out of 1000).
For example, for metals like Li there is no such problem at all. Also metal-insulator-metal
systems in the tunneling regime do not show the aforementioned inconsistencies.
I would be grateful, if somebody could give an explanation, as to how the epsproj parameter
can influence the result of the calculation in such a dramatic way and how one can decide
on the optimal value of this parameter.
With kind regards,
Vladislav Borisov
Martin Luther University Halle-Wittenberg
Von-Seckendorff-Platz 1, Room 1.17
06120, Halle (Saale), Germany
Tel No: +49 (0) 345 55-25448
Fax No: +49 (0) 345 55-25446
Email: vladislav.borisov at physik.uni-halle.de
More information about the users
mailing list