[Pw_forum] Transmission calculation for simple metals
Dear all, thank you very much for your kind help and the suggestions. As it occurs for the system I study, larger values of ewind, indeed, solve the problem with the transmission at some k-points, and now the convergence is achieved even for smaller epsproj < 1.e-7. I also agree that the optimal combination of parameters (ewind, epsproj) that provides a good convergence might be different in each case, as we noticed from the previous tests for other systems. Regarding the question about the structure of cobalt: > Finally, a word about the crystal structure. Are you sure that?s what you > want? > The neighbors of the Co atoms seem to have different bond distances. Maybe > you need > to choose another value for celldm(3)? In fact, such tetragonally distorted fcc structure is exactly what we need in our study. I have an additional question about the delgep parameter. According to its description, it is used for stability reasons when the eigenvalue problem is solved, and the default value is 5.e-10. It is also clear that the minimal possible value should be used, as long as the code doesn't crash. However, when I use the following setup for the calculation of cobalt ewind= 400.d0, epsproj = 1.d-10, delgep = 5.d-10, nz1 = 22 the calculation ends with an error stopping ... %%% Error in routine transmit (1029): problems with the linear system %%% Getting back to values of the order of 1.e-7 solves the problem. Is it acceptable to use such relatively large values of delgep? 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
[Pw_forum] Transmission calculation for simple metals
Dear all For this simple case of extended in the XY plane system the procedure of 2d basis reduction controlled by parameters ewind and epsproj should not be very efficient, in fact it is better if you use the full 2d basis, which is in this case n2d=271... You can do that specifying very big value for ewind, say ewind=400. I would also reduce delgep parameter to say delgep=5.d-10. It needs to be set to bigger values if the code crashes... good luck, Alex 2014-07-18 16:39 GMT+02:00 Sclauzero Gabriele < gabriele.sclauzero at mat.ethz.ch>: > Dear Vladislav, > > I mostly agree with what Nicki said here below. I also believe that in > your case the problem is the ewind value, which is too small and can lead > to some weirdnesses in the 2D-basis set reduction. You should try at least > 4.0 and check convergence as suggested by Nicki. > In my experience, the choice of epsproj depends a lot on the system. Even > values around 1.d-5 could assure a decent convergence, unless the basis set > reduction went bananas (e.g., because of a too small ewind). > Also, if you push epsproj very low, but you keep ewind very small, then > you could also get into trouble. > In normal calculations, I never found the need to increase the nz1 from > its default. > > Finally, a word about the crystal structure. Are you sure that?s what you > want? The neighbors of the Co atoms seem to have different bond distances. > Maybe you need to choose another value for celldm(3)? > > HTH > > > GS > > > > > > Il giorno 18/lug/2014, alle ore 12:53, nicvok ha > scritto: > > > The parameters epsproj and ewind control the amount of basis functions > > used in the underlying complex > > bandstructure (CBS) calculation in your case 121; cf. Choi ( > http://journals.aps.org/prb/pdf/10.1103/PhysRevB.59.2267 > > ) and > > DalCorso et al. ( > http://journals.aps.org/prb/abstract/10.1103/PhysRevB.74.045429 > > ). So one should take a > > look at the CBS before and check for reasonableness and convergence. > > Then adapt step by step epsproj and ewind (even more nz1) and check > > for convergence of the CBS. > > In your case ewind=2 might be okay, nevertheless I would slightly > > increase this (3-5). Did you ever tried > > some meaningful epsproj< 1.d-7, which should be a good value? The > > number of integral points with 22 seems to > > be okay. That it worked for other systems could be by accident. Again, > > as always, one finds the optimal > > value of the parameters, by checking for convergence of the underlying > > physics. > > > > bests Nicki > > > > - > > Nicki Frank Hinsche, Dr. rer. nat. > > Institute of physics - Theoretical physics, > > Martin-Luther-University Halle-Wittenberg, > > Von-Seckendorff-Platz 1, Room 1.07 > > D-06120 Halle/Saale, Germany > > Tel.: ++49 345 5525460 > > - > > ___ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://pwscf.org/mailman/listinfo/pw_forum > > > Dr. Gabriele Sclauzero > Materials Theory - ETHZ > ETH Zurich, HIT G 43.2 > Wolfgang-Pauli-Str. 27 > 8093 Z?rich, Switzerland > > Phone +41 44 633 94 10 > Fax +41 44 633 14 59 > gabriele.sclauzero at mat.ethz.ch > www.theory.mat.ethz.ch > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -- next part -- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140718/8a1bfa77/attachment.html
[Pw_forum] Transmission calculation for simple metals
Dear Vladislav, I mostly agree with what Nicki said here below. I also believe that in your case the problem is the ewind value, which is too small and can lead to some weirdnesses in the 2D-basis set reduction. You should try at least 4.0 and check convergence as suggested by Nicki. In my experience, the choice of epsproj depends a lot on the system. Even values around 1.d-5 could assure a decent convergence, unless the basis set reduction went bananas (e.g., because of a too small ewind). Also, if you push epsproj very low, but you keep ewind very small, then you could also get into trouble. In normal calculations, I never found the need to increase the nz1 from its default. Finally, a word about the crystal structure. Are you sure that?s what you want? The neighbors of the Co atoms seem to have different bond distances. Maybe you need to choose another value for celldm(3)? HTH GS Il giorno 18/lug/2014, alle ore 12:53, nicvok ha scritto: > The parameters epsproj and ewind control the amount of basis functions > used in the underlying complex > bandstructure (CBS) calculation in your case 121; cf. Choi > (http://journals.aps.org/prb/pdf/10.1103/PhysRevB.59.2267 > ) and > DalCorso et al. > (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.74.045429 > ). So one should take a > look at the CBS before and check for reasonableness and convergence. > Then adapt step by step epsproj and ewind (even more nz1) and check > for convergence of the CBS. > In your case ewind=2 might be okay, nevertheless I would slightly > increase this (3-5). Did you ever tried > some meaningful epsproj< 1.d-7, which should be a good value? The > number of integral points with 22 seems to > be okay. That it worked for other systems could be by accident. Again, > as always, one finds the optimal > value of the parameters, by checking for convergence of the underlying > physics. > > bests Nicki > > - > Nicki Frank Hinsche, Dr. rer. nat. > Institute of physics - Theoretical physics, > Martin-Luther-University Halle-Wittenberg, > Von-Seckendorff-Platz 1, Room 1.07 > D-06120 Halle/Saale, Germany > Tel.: ++49 345 5525460 > - > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum Dr. Gabriele Sclauzero Materials Theory - ETHZ ETH Zurich, HIT G 43.2 Wolfgang-Pauli-Str. 27 8093 Z?rich, Switzerland Phone +41 44 633 94 10 Fax +41 44 633 14 59 gabriele.sclauzero at mat.ethz.ch www.theory.mat.ethz.ch
[Pw_forum] Transmission calculation for simple metals
The parameters epsproj and ewind control the amount of basis functions used in the underlying complex bandstructure (CBS) calculation in your case 121; cf. Choi (http://journals.aps.org/prb/pdf/10.1103/PhysRevB.59.2267 ) and DalCorso et al. (http://journals.aps.org/prb/abstract/10.1103/PhysRevB.74.045429 ). So one should take a look at the CBS before and check for reasonableness and convergence. Then adapt step by step epsproj and ewind (even more nz1) and check for convergence of the CBS. In your case ewind=2 might be okay, nevertheless I would slightly increase this (3-5). Did you ever tried some meaningful epsproj< 1.d-7, which should be a good value? The number of integral points with 22 seems to be okay. That it worked for other systems could be by accident. Again, as always, one finds the optimal value of the parameters, by checking for convergence of the underlying physics. bests Nicki - Nicki Frank Hinsche, Dr. rer. nat. Institute of physics - Theoretical physics, Martin-Luther-University Halle-Wittenberg, Von-Seckendorff-Platz 1, Room 1.07 D-06120 Halle/Saale, Germany Tel.: ++49 345 5525460 -
[Pw_forum] Transmission calculation for simple metals
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:
calculation='scf',
restart_mode='from_scratch',
pseudo_dir = '/scratch/vborisov/pseudo/',
outdir='/scratch/vborisov/tmp/Co-Transmission/',
prefix='fct-2',
wf_collect=.true.
/
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
/
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:
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 =0.000 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 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 0.000 0.000
-0.0964682 -0.000 0.000
-0.0964689 -0.000 0.000
-0.0964705 0.000 0.000
-0.0964798 -0.000 0.000
-0.0965107 0.000 0.000
-0.0965482 0.000 0.000
-0.0966171 0.000 0.000
-0.0968639 0.000 0.000
-0.0985616 0.000 0.000
-0.1341194 0.003 0.000
-0.1855624 0.002 0.000
-0.2949790 0.002 0.000
-0.3297361 0.000 0.000
0.4517894 -0.001 0.000
Left moving states:
k1(2pi/a) k2(2pi/a) E-Ef (eV)
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964682 -0.000 0.000
0.0964689 0.000 0.000
0.0964705 0.000 0.000
0.0964798 -0.000 0.000
0.0965107 0.000 0.000
0.0965482 0.000 0.000
0.0966171 0.000 0.000
0.0968639 0.000 0.000
0.0985616 0.000 0.000
0.1341194 0.003 0.000
0.1855624 0.002 0.000
0.2949790 0.002 0.000
0.3297361 0.000 0.000
-0.4517894 -0.001 0.000
to transmit
Band j to band i transmissions and reflections:
j i |T_ij|^2|R_ij|^2
1 --> 1 1.0 0.0
1 --> 2 0.0 0.0
1 --> 3 0.0 0.0
1 --> 4 0.0 0.0
1 --> 5 0.0 0.0
1 --> 6 0.0 0.0
1 --> 7 0.0 0.0
1 --> 8 0.0 0.0
1 --> 9 0.0 0.0
1 -->10 0.0 0.0
1 -->11 0.0 0.0
1 -->12 0.0 0.0
1 -->13 0.0 0.0
1 -->14 0.0 0.0
1 -->15 0.0 0.0
1 -->16 0.0 0.0
1 -->17 0.0 0.0
1 -->18 0.0
[Pw_forum] transmission calculation
Quoting Manoj Srivastava :
> Dear PWSCF users and developers,
> I have been trying to do the conductance calculation for the twin
> boundary of Cu. I compared my results with previously done calculations
> and for most K points the transmission coefficients match up very well.
> But there are some k points that I get transmission coefficients more than
> 1! This is not reasonable, as the maximum value of transmission
> coefficient could be 1.I am getting 1.000345, and similar for other k
> points.
Which k-points? How many channels are there? Please send me the output
file or post the relevant part of it.
> Do you think transmission coefficients being more than 1 is just
> numerical error of the code or there is something wrong with my input
> file? Attached is the input file for lead and scatterign region -
Transmission coefficients should be between 0 and 1. In the code there
are many levels of approximation. Some of them may affect the results.
Usually the two relevant parameters one needs to adjust are epsproj
and ewind. Why are you tweaking the others? Have you tried the default?
> ecutwfc =150.0,
Why such a high value? You are using US, aren't you?
> ATOMIC_POSITIONS
> Cu 0.0 0.00.0
> Cu -0.5 0.2886751340.81649658
> Cu -1.0 0.5773502691.632993162
>
> K_POINTS (automatic)
> 6 6 8 1 1 1
> CELL_PARAMETERS {hexagonal}
> 1.0 0.00.0
> -0.5 0.8660254037844386 0.0
> 0.0 0.0 2.449489743
This shouldn't be an issue, but you could try to use ibrav=4 instead
of ibrav=0 and specify atomic positions such that all atoms are inside
the first primitive cell (i.e. the one with R=0)
>
> /
> 6
> 0.500 -0.500 1
> 4.2584095E-17 0.500 1
Why don't you specify 0.0 instead? Should not matter anyway.
Gabriele Sclauzero
SISSA & Democritos
> 0.250000.000 1
> 0.167 0.167 1
> -1.2775231E-16 -0.250 1
> 0.250 -0.251 1
> 1
> 0.0
>
>
> Regards,
> Manoj Srivastava
> University of Florida,
> Gainesville, FL
>
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
SISSA Webmail https://webmail.sissa.it/
Powered by Horde http://www.horde.org/
[Pw_forum] transmission calculation
Dear PWSCF users and developers,
I have been trying to do the conductance calculation for the twin
boundary of Cu. I compared my results with previously done calculations
and for most K points the transmission coefficients match up very well.
But there are some k points that I get transmission coefficients more than
1! This is not reasonable, as the maximum value of transmission
coefficient could be 1.I am getting 1.000345, and similar for other k
points. Do you think transmission coefficients being more than 1 is just
numerical error of the code or there is something wrong with my input
file? Attached is the input file for lead and scatterign region -
SCF for the LEFT lead-
calculation='scf'
pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
outdir='./',
prefix='lcu',
/
ibrav =0,
celldm(1)=4.82,
nat= 3,
ntyp= 1,
ecutwfc =150.0,
occupations='smearing',
smearing='gaussian',
degauss=0.02,
ecutrho=500
/
conv_thr = 1.0e-8
mixing_beta=0.7
/
ATOMIC_SPECIES
Cu 63.55 Cu.pz-d-rrkjus.UPF
ATOMIC_POSITIONS
Cu 0.0 0.00.0
Cu -0.5 0.2886751340.81649658
Cu -1.0 0.5773502691.632993162
K_POINTS (automatic)
6 6 8 1 1 1
CELL_PARAMETERS {hexagonal}
1.0 0.00.0
-0.5 0.8660254037844386 0.0
0.0 0.0 2.449489743
>>
SCF for the RIGHT lead-
calculation='scf'
pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
outdir='./',
prefix='rcu',
/
ibrav =0,
celldm(1)=4.82,
nat= 3,
ntyp= 1,
ecutwfc =150.0,
occupations='smearing',
smearing='gaussian',
degauss=0.02,
ecutrho=500
/
conv_thr = 1.0e-8
mixing_beta=0.7
/
ATOMIC_SPECIES
Cu 63.55 Cu.pz-d-rrkjus.UPF
ATOMIC_POSITIONS
Cu 0.0 0.00.0
Cu 0.5 -0.2886751340.81649658
Cu 1.0 -0.5773502691.632993162
K_POINTS (automatic)
6 6 8 1 1 1
CELL_PARAMETERS {hexagonal}
1.0 0.00.0
-0.5 0.8660254037844386 0.0
0.0 0.0 2.449489743
>
SCF for SCATTERING region-
calculation='scf'
pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
outdir='./',
prefix='scu',
/
ibrav =0,
celldm(1)=4.82,
nat= 12,
ntyp= 1,
ecutwfc =150.0,
occupations='smearing',
smearing='gaussian',
degauss=0.02,
ecutrho=500
/
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 -0.5 0.288675134 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 2.0 -1.154700538 6.531972647
Cu 1.5 -0.866025404 7.348469228
Cu 1.0 -0.577350269 8.164965809
Cu 0.5 -0.288675134 8.981462390
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 9.797958971
>>
input file for conductance part-
outdir='./'
prefixs='scu'
prefixl='lcu'
prefixr='rcu'
tran_file ='trans.twin'
ikind=2
ecut2d=200
energy0=0.0
denergy=0.0
ewind=101.d0
epsproj=1.d-6
nz1=25
bds=3.265986324
/
6
0.500 -0.500 1
4.2584095E-17 0.500 1
0.250000.000 1
0.167 0.167 1
-1.2775231E-16 -0.250 1
0.250 -0.251 1
1
0.0
Regards,
Manoj Srivastava
University of Florida,
Gainesville, FL
[Pw_forum] transmission calculation
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 -
>
>
> calculation='scf'
> pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
> outdir='./',
> prefix='cus',
> /
>
> ibrav =0,
> celldm(1)=4.82,
> nat= 10,
> ntyp= 1,
> ecutwfc =50.0,
> occupations='smearing',
> smearing='gaussian',
> degauss=0.02,
> ecutrho=500
> /
>
> 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 -
>
>
> 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
> 0.00 0.00 1
> 0.500 -0.500 1
>
> 1
> 0.0
>
> Thank you for your attention.
>
> Regards,
> Manoj Srivastava
> Graduate Student
> Department of Physics
> University of Florida, Gainesville, FL
>
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
--
Alexander Smogunov
Email: smogunov at sissa.it
Home page: http://people.sissa.it/~smogunov
[Pw_forum] transmission calculation
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.
Does it happen also when you do not use G_perp basis reduction? Can you try
again the CBS
and the transmission calculation without specifying ecut2d, nz1 and putting
ewind=1.d3?
Better, first check the size of the reduced basis using
grep n2d
and see if they are very different (or if the second is too low with respect to
the size
of the whole basis set).
Also try to understand which of the two results (kz vectors) is correct, by
comparing the
real part of kz with the band structure from pw.x
GS
> 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 -
>
>
> calculation='scf'
> pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
> outdir='./',
> prefix='cus',
> /
>
> ibrav =0,
> celldm(1)=4.82,
> nat= 10,
> ntyp= 1,
> ecutwfc =50.0,
> occupations='smearing',
> smearing='gaussian',
> degauss=0.02,
> ecutrho=500
> /
>
> 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 -
>
>
> 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
> 0.00 0.00 1
> 0.500 -0.500 1
>
> 1
> 0.0
>
> Thank you for your attention.
>
> Regards,
> Manoj Srivastava
> Graduate Student
> Department of Physics
> University of Florida, Gainesville, FL
>
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
--
o o
| Gabriele Sclauzero, PhD Student |
| c/o: SISSA & CNR-INFM Democritos, |
|via Beirut 2-4, 34014 Trieste (Italy) |
| email: sclauzer at sissa.it |
| phone: +39 040 3787 511 |
| skype: gurlonotturno |
o o
[Pw_forum] transmission calculation
In data 30 aprile 2009 alle ore 13:23:25, Manoj Srivastava ha scritto: > 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 - I'm no expert in transimission calculation, but I have had a look at your scf input file for the lead region, using XCrysDen, and I've noticed tha tlayers 4 and 5 are aligned in a strange way, reducing the system symmetry. Are you sure you have done it on purpose? Have you tried checking your input files with XCD? best regards -- Lorenzo Paulatto SISSA & DEMOCRITOS (Trieste) phone: +39 040 3787 511 skype: paulatz www: http://people.sissa.it/~paulatto/ *** save italian brains *** http://saveitalianbrains.wordpress.com/
[Pw_forum] transmission calculation
Dear Gabriele,
Thanks for answering.
On Thu, 30 Apr 2009, Gabriele Sclauzero wrote:
> 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.
>
> Does it happen also when you do not use G_perp basis reduction? Can you try
> again the CBS
> and the transmission calculation without specifying ecut2d, nz1 and putting
> ewind=1.d3?
Yes, I have tried this. No difference, the kz value for left lead gets
changed, when i switch from ikind=0 to ikind=2.
>
> Better, first check the size of the reduced basis using
>
> grep n2d
>
> and see if they are very different (or if the second is too low with respect
> to the size
> of the whole basis set).
> Also try to understand which of the two results (kz vectors) is correct, by
> comparing the
> real part of kz with the band structure from pw.x
The one with ikind=0 is correct.
>
>
> GS
>
>
> > 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 -
> >
> >
> > calculation='scf'
> > pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
> > outdir='./',
> > prefix='cus',
> > /
> >
> > ibrav =0,
> > celldm(1)=4.82,
> > nat= 10,
> > ntyp= 1,
> > ecutwfc =50.0,
> > occupations='smearing',
> > smearing='gaussian',
> > degauss=0.02,
> > ecutrho=500
> > /
> >
> > 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 -
> >
> >
> > 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
> > 0.00 0.00 1
> > 0.500 -0.500 1
> >
> > 1
> > 0.0
> >
> > Thank you for your attention.
> >
> > Regards,
> > Manoj Srivastava
> > Graduate Student
> > Department of Physics
> > University of Florida, Gainesville, FL
> >
> > ___
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
>
> --
>
>
> o o
> | Gabriele Sclauzero, PhD Student |
> | c/o: SISSA & CNR-INFM Democritos, |
> |via Beirut 2-4, 34014 Trieste (Italy) |
> | email: sclauzer at sissa.it |
> | phone: +39 040 3787 511 |
> | skype: gurlonotturno |
> o o
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
[Pw_forum] transmission calculation
Dear Lorenzo, Thank you for answering. Layers 4 and 5 are supposed be like that, it is done on purpose. The file I provided was not for the lead but for the scattering region. I have visualized my structure, it looks ok. Regards, Manoj On Thu, 30 Apr 2009, Lorenzo Paulatto wrote: > In data 30 aprile 2009 alle ore 13:23:25, Manoj Srivastava > ha scritto: > > 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 - > > I'm no expert in transimission calculation, but I have had a look at your > scf input file for the lead region, using XCrysDen, and I've noticed tha > tlayers 4 and 5 are aligned in a strange way, reducing the system > symmetry. Are you sure you have done it on purpose? Have you tried > checking your input files with XCD? > > best regards > > > -- > Lorenzo Paulatto > SISSA & DEMOCRITOS (Trieste) > phone: +39 040 3787 511 > skype: paulatz > www: http://people.sissa.it/~paulatto/ > > *** save italian brains *** > http://saveitalianbrains.wordpress.com/ > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
[Pw_forum] transmission calculation
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 -
calculation='scf'
pseudo_dir = '/home/manoj/espresso-4.0.1/pseudo',
outdir='./',
prefix='cus',
/
ibrav =0,
celldm(1)=4.82,
nat= 10,
ntyp= 1,
ecutwfc =50.0,
occupations='smearing',
smearing='gaussian',
degauss=0.02,
ecutrho=500
/
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 -
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
0.00 0.00 1
0.500 -0.500 1
1
0.0
Thank you for your attention.
Regards,
Manoj Srivastava
Graduate Student
Department of Physics
University of Florida, Gainesville, FL
[Pw_forum] Transmission calculation using PWCOND
Thank you Alexander!
-Manoj
On Fri, 3 Apr 2009, Alexander Smogunov wrote:
> Dear Manoj
>
> On Wednesday 01 April 2009 22:57, Manoj Srivastava wrote:
> > Dear PWSCF users and developers,
> > I have been trying to understand the PWCOND code for transmission
> > calculation, basically 'transmit.f90' file. The wavefunction in the left
> > lead, right lead and scattering region is given by -
> >
> >psi_k+sum_{k'}r_{kk'}psi_k'
> > psi= sum_{n} a_n psi_n+ sum_{\alpha l m} C_{\alpha l m}psi_{\alpha l m}
> >sum_{k'}t_{kk'}psi_k'
> >
> > The above expression is from Choi & Ihm's paper, on which I believe PWCOND
> > is based on. Now undetermined coefficients in above expression are
> > r_{kk'}, a_n, C_{\alpha,l,m}, t_kk'. I am confused on code evaluates these
> > coefficients. My understanding is you first get the wavefunction in the
> > leads and then solve scattering region the same way to get the
> > wavefunction in scattering region, so at this point you have already
> > determined a_n and C_{\alpha,l,m}. At last do boundary matching condition
> > between leads and scattering region to get reflection and transmission
> > coefficient. Am I right?
> No, the scattering state (SS) is completely determined by unknown
> coefficients which are: {r_kk', a_n, a_alpha, t_kk'}, the first defines the
> SS in the left lead, the two next in the scattering region, and the last one
> in the right lead. What you have found before are just basis solutions phi_n
> and phi_alpha of the Sroedinger eq. in the scattering region over which you
> expand the SS with coefficients (unknown yet) a_n and a_alpha.
>
> Hope this helps,
> Alexander
>
> > My thinking is based on simple quantum mechanics
> > scattering problem where we solve schrodinger's equation in each region
> > and then do boundary matching to get reflection and transmission
> > coefficients.
> >
> > Now looking at the subroutine 'transmit.f90', this does not appear to be
> > the case. It seems as if we are solving the Schrodinger's equation in the
> > scattering region and doing boundary matching at the same time. Using a
> > big matrix and solving something like AX=B. Would anybody mind explaing
> > what's going on in subroutine transmit.f90?
> >
> > Regards,
> > Manoj Srivastava
> > Physics Graduate Student
> > University Of Florida, Gainesville, FL
> >
> > ___
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
[Pw_forum] Transmission calculation using PWCOND
Dear Manoj
On Wednesday 01 April 2009 22:57, Manoj Srivastava wrote:
> Dear PWSCF users and developers,
> I have been trying to understand the PWCOND code for transmission
> calculation, basically 'transmit.f90' file. The wavefunction in the left
> lead, right lead and scattering region is given by -
>
>psi_k+sum_{k'}r_{kk'}psi_k'
> psi= sum_{n} a_n psi_n+ sum_{\alpha l m} C_{\alpha l m}psi_{\alpha l m}
>sum_{k'}t_{kk'}psi_k'
>
> The above expression is from Choi & Ihm's paper, on which I believe PWCOND
> is based on. Now undetermined coefficients in above expression are
> r_{kk'}, a_n, C_{\alpha,l,m}, t_kk'. I am confused on code evaluates these
> coefficients. My understanding is you first get the wavefunction in the
> leads and then solve scattering region the same way to get the
> wavefunction in scattering region, so at this point you have already
> determined a_n and C_{\alpha,l,m}. At last do boundary matching condition
> between leads and scattering region to get reflection and transmission
> coefficient. Am I right?
No, the scattering state (SS) is completely determined by unknown
coefficients which are: {r_kk', a_n, a_alpha, t_kk'}, the first defines the
SS in the left lead, the two next in the scattering region, and the last one
in the right lead. What you have found before are just basis solutions phi_n
and phi_alpha of the Sroedinger eq. in the scattering region over which you
expand the SS with coefficients (unknown yet) a_n and a_alpha.
Hope this helps,
Alexander
> My thinking is based on simple quantum mechanics
> scattering problem where we solve schrodinger's equation in each region
> and then do boundary matching to get reflection and transmission
> coefficients.
>
> Now looking at the subroutine 'transmit.f90', this does not appear to be
> the case. It seems as if we are solving the Schrodinger's equation in the
> scattering region and doing boundary matching at the same time. Using a
> big matrix and solving something like AX=B. Would anybody mind explaing
> what's going on in subroutine transmit.f90?
>
> Regards,
> Manoj Srivastava
> Physics Graduate Student
> University Of Florida, Gainesville, FL
>
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] Transmission calculation using PWCOND
Dear PWSCF users and developers,
I have been trying to understand the PWCOND code for transmission
calculation, basically 'transmit.f90' file. The wavefunction in the left
lead, right lead and scattering region is given by -
psi_k+sum_{k'}r_{kk'}psi_k'
psi= sum_{n} a_n psi_n+ sum_{\alpha l m} C_{\alpha l m}psi_{\alpha l m}
sum_{k'}t_{kk'}psi_k'
The above expression is from Choi & Ihm's paper, on which I believe PWCOND
is based on. Now undetermined coefficients in above expression are
r_{kk'}, a_n, C_{\alpha,l,m}, t_kk'. I am confused on code evaluates these
coefficients. My understanding is you first get the wavefunction in the
leads and then solve scattering region the same way to get the
wavefunction in scattering region, so at this point you have already
determined a_n and C_{\alpha,l,m}. At last do boundary matching condition
between leads and scattering region to get reflection and transmission
coefficient. Am I right? My thinking is based on simple quantum mechanics
scattering problem where we solve schrodinger's equation in each region
and then do boundary matching to get reflection and transmission
coefficients.
Now looking at the subroutine 'transmit.f90', this does not appear to be
the case. It seems as if we are solving the Schrodinger's equation in the
scattering region and doing boundary matching at the same time. Using a
big matrix and solving something like AX=B. Would anybody mind explaing
what's going on in subroutine transmit.f90?
Regards,
Manoj Srivastava
Physics Graduate Student
University Of Florida, Gainesville, FL
