[Pw_forum] Slow calculation of (5, 5) CNT transmission and complex bands.

[Gabriele Sclauzero]

Il giorno 09/ago/2011, alle ore 19.02, chengyu yang ha scritto:

> Dear Dr. Sclaizero and all,
>          The example is from the example 1 ,in the Complex band structures and ballistic conductance in the hands-on tutorial of quantum espresso, and it's about the bandstructure of bulk Al along the 001 direction. I am now pasting the input script for the nscf calculation here, at the end you would see the 50 K points:

OK, so you're speaking of bulk Al.

(from your previous email)
>      (2) In the conductance example for Al, I see they used 50 k points to get a bandstructure, and I was wondering how did they get them?

It should be just a straight k-point path connecting Gamma to X in the BZ of fcc Al.

> I can only find at most 10 high symmetry points for Al.

In this 50 k-point path there should be just 2 high-symmetry points (Gamma and X), I don't understand why you bother about the other points.

> Do we need the same amount/scale of K point ? If so, how?

The number of points you want to include along the transport direction to check up to which accuracy the band structure of PWscf is reproduced by PWcond is up to you. I would use, let's say, 20-30 points in the nscf calculation, such that the successive bands.x run can resolve the band-crossings and one can plot a nice band structure with lines. 

Then you need to perform a PWcond run for a set of scattering energies {e_1, e_2,...} in the intersting range and superimpose the resulting (e_i,k) points (for k real) to the previously obtained band structure. These points should fall on the lines corresponding to the PWscf band structure.


HTH

Mr. SclaUzero


> 
>           al.nscf.in
> 
> 
>  &control
>     calculation='nscf'
>     restart_mode='from_scratch',
>     pseudo_dir = '$PSEUDO_DIR',
>     outdir='$TMP_DIR'
>     prefix='al'
>  /
>  &system
>     ibrav = 6, 
>     celldm(1) =5.3, 
>     celldm(3) =1.414, 
>     nat= 2, 
>     ntyp= 1,
>     ecutwfc = 15.0, 
>     occupations='smearing', 
>     smearing='methfessel-paxton', 
>     degauss=0.01
>  /
>  &electrons
>     conv_thr = 1.0e-8
>     mixing_beta = 0.7
>  /
> ATOMIC_SPECIES
>  Al 26.98 Al.vbc.UPF 
> ATOMIC_POSITIONS
>  Al 0. 0. 0.0
>  Al 0.5 0.5 0.707
> K_POINTS 
> 50
> 0.00   0.00       0.00000000      0.00000000
> 0.00   0.00       0.00721538      0.00721538
> 0.00   0.00       0.01443075      0.01443075
> 0.00   0.00       0.02164613      0.02164613
> 0.00   0.00       0.02886150      0.02886150
> 0.00   0.00       0.03607688      0.03607688
> 0.00   0.00       0.04329225      0.04329225
> 0.00   0.00       0.05050763      0.05050763
> 0.00   0.00       0.05772300      0.05772300
> 0.00   0.00       0.06493838      0.06493838
> 0.00   0.00       0.07215375      0.07215375
> 0.00   0.00       0.07936913      0.07936913
> 0.00   0.00       0.08658450      0.08658450
> 0.00   0.00       0.09379988      0.09379988
> 0.00   0.00       0.10101525      0.10101525
> 0.00   0.00       0.10823063      0.10823063
> 0.00   0.00       0.11544601      0.11544601
> 0.00   0.00       0.12266138      0.12266138
> 0.00   0.00       0.12987676      0.12987676
> 0.00   0.00       0.13709213      0.13709213
> 0.00   0.00       0.14430751      0.14430751
> 0.00   0.00       0.15152288      0.15152288
> 0.00   0.00       0.15873826      0.15873826
> 0.00   0.00       0.16595363      0.16595363
> 0.00   0.00       0.17316901      0.17316901
> 0.00   0.00       0.18038438      0.18038438
> 0.00   0.00       0.18759976      0.18759976
> 0.00   0.00       0.19481513      0.19481513
> 0.00   0.00       0.20203051      0.20203051
> 0.00   0.00       0.20924588      0.20924588
> 0.00   0.00       0.21646126      0.21646126
> 0.00   0.00       0.22367663      0.22367663
> 0.00   0.00       0.23089201      0.23089201
> 0.00   0.00       0.23810739      0.23810739
> 0.00   0.00       0.24532276      0.24532276
> 0.00   0.00       0.25253814      0.25253814
> 0.00   0.00       0.25975351      0.25975351
> 0.00   0.00       0.26696889      0.26696889
> 0.00   0.00       0.27418426      0.27418426
> 0.00   0.00       0.28139964      0.28139964
> 0.00   0.00       0.28861501      0.28861501
> 0.00   0.00       0.29583039      0.29583039
> 0.00   0.00       0.30304576      0.30304576
> 0.00   0.00       0.31026114      0.31026114
> 0.00   0.00       0.31747651      0.31747651
> 0.00   0.00       0.32469189      0.32469189
> 0.00   0.00       0.33190726      0.33190726
> 0.00   0.00       0.33912264      0.33912264
> 0.00   0.00       0.34633802      0.34633802
> 0.00   0.00       0.35355339      0.35355339
> 
> Thank you!
> Best regards.
> 
> Chengyu Yang
> MMAE, University of Central Florida
> 
> 
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum


§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20110810/7c4a6f3c/attachment.html>