[Pw_forum] transmission calculation

[Alexander Smogunov]

Dear Manoj 
Please provide also scf files for the leads.
Note that in the case ikind=2 (different leads) the scattering file
should be a double unit cell i.e. should contain the scattering barrier
+ some portion of the right lead + the scattering barrier in order to
have regular periodicity in the z direction. You should also provide
bds parameter which says where the scattering barrier ends (while it
should start from 0). 
Regards, Alexander

 
On Thu, 2009-04-30 at 07:23 -0400, Manoj Srivastava wrote:
> 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
> 
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-- 
Alexander Smogunov 
Email:     smogunov at sissa.it
Home page: http://people.sissa.it/~smogunov