[Pw_forum] transmission calculation

[Manoj Srivastava]

Dear PWSCF users and developers,
 I have tried to do a transmission calcuation and not getting right
results. I have tried to figure out the reason behind this and realized
that in my set up for some reason the Bloch waves in left lead get changed
resulting wrong transmission. By this I meant that, if I just try to
calculate complex band of the left lead, I have a kz for each kx,ky and E
but when I am doing transmission calculation, the Bloch's wave in the same
lead has different kz for the same kx,ky and E, which does not make sense
as why should the Bloch's wave in lead get affected by the presence of
scattering region? For the right lead kz remains the same in both cases
though, which I believe how it should be. 
 I did this for several cases, I interchanged right and left leads,
increased number of atoms in the scattering region, chose scattering
region in different way, and everytime kz of left lead changes. Following
is my input file for the scattering region - 

scf part -

&control
    calculation='scf'
    pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
    outdir='./',
    prefix='cus',
 /
 &system
    ibrav =0,
    celldm(1)=4.82,
    nat= 10,
    ntyp= 1,
    ecutwfc =50.0,
    occupations='smearing',
    smearing='gaussian',
    degauss=0.02,
    ecutrho=500
 /
 &electrons
    conv_thr = 1.0e-8
    mixing_beta=0.7
/
ATOMIC_SPECIES
 Cu 63.55  Cu.pz-d-rrkjus.UPF
ATOMIC_POSITIONS
  Cu  0.0   0.0         0.0
  Cu -0.5   0.288675134 0.816496581
  Cu -1.0   0.577350269 1.632993162
  Cu -1.5   0.866025404 2.449489743
  Cu  0.0   0.0         3.265986324
  Cu  0.5  -0.288675134 4.082482905
  Cu  1.0  -0.577350269 4.898979486
  Cu  1.5  -0.866025404 5.715476066
  Cu  1.0  -0.577350269 6.531972647
  Cu  0.5  -0.288675134 7.348469228
 K_POINTS (automatic)
6 6 4 1 1 1
CELL_PARAMETERS {hexagonal}
 1.0   0.0         0.0
-0.5   0.866025403 0.0
 0.0   0.0         8.16496581



conductance part -

&inputcond
    outdir='./'
    prefixl='cul'
    prefixr='cur'
    prefixs='cus'
    tran_file ='trans.twin'
    ikind=2
    ecut2d=50
    energy0=0.0
    denergy=0.0
    ewind=5.d0
    epsproj=1.d-6
    nz1=25
 /
  2
  0.000000       0.000000               1
  0.5000000     -0.5000000               1

1
0.0

Thank you for your attention. 

Regards, 
Manoj Srivastava
Graduate Student
Department of Physics
University of Florida, Gainesville, FL