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

Gabriele Sclauzero gabriele.sclauzero at epfl.ch
Tue Aug 2 11:35:50 CEST 2011


Hello,

Il giorno 28/lug/2011, alle ore 23.03, chengyu yang ha scritto:

> Dear All,
>          I am trying to calculate the complex bands and the transmission of a (5,5) defectless carbon nanotube using PWCOND.x, however, the calculation process is very slow and I can see it kind of stopped at the point:  ngper, shell number =         2809         299.

Your value of ngper is quite large for this kind of calculations, you can't afford it without using a lot of processors in a parallel calculation. Moreover,  as far as I know the calculation of the complex bands is not completely parallelized at the moment, hence if your leads have a very large cross section and contain really a lot of atoms, I'm afraid that the calculation is hardly feasible with the current implementation.

In your case, the calculation should be feasible with 8-16 processors in parallel (if nodes have enough memory), but only if you use USPP, so that you will be able to reduce the ecutwfc down to 30-35 Ry.

In the PWcond input file I would reduce epsproj to 10^-5 or 10^-6, depending on the level of accuracy required (but you should do a small test on this).


HTH

GS


>          My input files are like this:
> 
>   ##################################################################################
> scf input file:
> 
> &CONTROL
>                  calculation = 'scf' ,
>                 restart_mode = 'from_scratch' ,
>                        prefix = '55' ,
>  /
>  &SYSTEM
>                        ibrav = 6,
>                    celldm(1) = 21.764541128,celldm(3)=0.213765379
>                          nat = 20,
>                         ntyp = 1,
>                      ecutwfc = 75 ,
>  /
>  &ELECTRONS
>                     conv_thr = 1.0d-8 ,
>                  mixing_beta = 0.7 ,
>  /
> ATOMIC_SPECIES
>     C   12.01100  C.pz-vbc.UPF 
> 
> ATOMIC_POSITIONS angstrom
> 
>   C        3.409595     0.000000    -1.231179
>   C        3.113484     1.389805    -1.231179
>   C        2.758420     2.004110    -0.000000
>   C        1.701954     2.954436    -0.000000
>   C        1.053623     3.242718    -1.231179
>   C       -0.359664     3.390572    -1.231179
>   C       -1.053623     3.242718    -0.000000
>   C       -2.283903     2.531625    -0.000000
>   C       -2.758420     2.004110    -1.231179
>   C       -3.335768     0.705684    -1.231179
>   C       -3.409595     0.000000    -0.000000
>   C       -3.113484    -1.389805    -0.000000
>   C       -2.758420    -2.004110    -1.231179
>   C       -1.701954    -2.954436    -1.231179
>   C       -1.053623    -3.242718     0.000000
>   C        0.359664    -3.390572     0.000000
>   C        1.053623    -3.242718    -1.231179
>   C        2.283903    -2.531625    -1.231179
>   C        2.758420    -2.004110     0.000000
>   C        3.335768    -0.705684     0.000000
> 
> 
>   
> 
> K_POINTS automatic 
>  1 1 5 0 0 0
> 
> 
> ###############################################################################
> 
> pwcond.in file:
> 
> 
> &inputcond
>     prefixl='55'
>     band_file ='bands.cnt55'
>     ikind=0
>     energy0=4.d0
>     denergy=-0.1d0
>     ewind=3.d0
>     epsproj=1.d-4
>     delgep = 1.d-9
>     cutplot = 3.d0
>  /
>     1
>     0.0 0.0 1.0
>     5
> 
> ###########################################################
> and the output file:
> 
>      GEOMETRY:
> 
>      lattice parameter (a_0)   =      21.7645  a.u.
>      the volume                =    2203.8697 (a.u.)^3
>      the cross section         =     473.6953 (a.u.)^2
>      l of the unit cell        =       0.2138 (a_0)
>      number of atoms/cell      =           20
>      number of atomic types    =            1
> 
>      crystal axes: (cart. coord. in units of a_0)
>                a(1) = (  1.0000  0.0000  0.0000 )  
>                a(2) = (  0.0000  1.0000  0.0000 )  
>                a(3) = (  0.0000  0.0000  0.2138 )  
> 
> 
>    Cartesian axes
> 
>      site n.     atom                  positions (a_0 units)
>           1           C   tau(  1)=(  0.2960  0.0000  0.1069  )
>           2           C   tau(  2)=(  0.2703  0.1207  0.1069  )
>           3           C   tau(  3)=(  0.2395  0.1740  0.2138  )
>           4           C   tau(  4)=(  0.1478  0.2565  0.2138  )
>           5           C   tau(  5)=(  0.0915  0.2816  0.1069  )
>           6           C   tau(  6)=( -0.0312  0.2944  0.1069  )
>           7           C   tau(  7)=( -0.0915  0.2816  0.2138  )
>           8           C   tau(  8)=( -0.1983  0.2198  0.2138  )
>           9           C   tau(  9)=( -0.2395  0.1740  0.1069  )
>          10           C   tau( 10)=( -0.2896  0.0613  0.1069  )
>          11           C   tau( 11)=( -0.2960  0.0000  0.2138  )
>          12           C   tau( 12)=( -0.2703 -0.1207  0.2138  )
>          13           C   tau( 13)=( -0.2395 -0.1740  0.1069  )
>          14           C   tau( 14)=( -0.1478 -0.2565  0.1069  )
>          15           C   tau( 15)=( -0.0915 -0.2816  0.2138  )
>          16           C   tau( 16)=(  0.0312 -0.2944  0.2138  )
>          17           C   tau( 17)=(  0.0915 -0.2816  0.1069  )
>          18           C   tau( 18)=(  0.1983 -0.2198  0.1069  )
>          19           C   tau( 19)=(  0.2395 -0.1740  0.2138  )
>          20           C   tau( 20)=(  0.2896 -0.0613  0.2138  )
> 
>      nr1s                      =          120
>      nr2s                      =          120
>      nr3s                      =           27
>      nrx1s                     =          120
>      nrx2s                     =          120
>      nrx3s                     =           27
>      nr1                       =          120
>      nr2                       =          120
>      nr3                       =           27
>      nrx1                      =          120
>      nrx2                      =          120
>      nrx3                      =           27
> 
>  _______________________________
>   Radii of nonlocal spheres: 
> 
>      type       ibeta     ang. mom.          radius (a_0 units)
>           C       1         0                    0.0593
> ----- General information -----
> 
> ----- Complex band structure calculation -----
> 
>      nrx                       =          120
>      nry                       =          120
>      nz1                       =           11
> 
> 
>      energy0               =         4.0E+00
>      denergy               =        -1.0E-01
>      nenergy               =          5
>      ecut2d                =         7.5E+01
>      ewind                 =         3.0E+00
>      epsproj               =         1.0E-04
> 
> 
>      number of k_|| points=    1
>                        cryst. coord. 
>         k(    1) = (   0.0000000   0.0000000), wk =   1.0000000
> ----- Information about left lead ----- 
> 
>      nocros                   =           10
>      noins                    =           10
>      norb                     =           30
>      norbf                    =           30
>      nrz                      =           27
> 
>       iorb      type   ibeta   ang. mom.   m       position (a_0)
>         1        1       1        0        1   taunew(   1)=(  0.2395  0.1740  0.0000)
>         2        1       1        0        1   taunew(   2)=(  0.1478  0.2565  0.0000)
>         3        1       1        0        1   taunew(   3)=( -0.0915  0.2816  0.0000)
>         4        1       1        0        1   taunew(   4)=( -0.1983  0.2198  0.0000)
>         5        1       1        0        1   taunew(   5)=( -0.2960  0.0000  0.0000)
>         6        1       1        0        1   taunew(   6)=( -0.2703 -0.1207  0.0000)
>         7        1       1        0        1   taunew(   7)=( -0.0915 -0.2816  0.0000)
>         8        1       1        0        1   taunew(   8)=(  0.0312 -0.2944  0.0000)
>         9        1       1        0        1   taunew(   9)=(  0.2395 -0.1740  0.0000)
>        10        1       1        0        1   taunew(  10)=(  0.2896 -0.0613  0.0000)
>        11        1       1        0        1   taunew(  11)=(  0.2960  0.0000  0.1069)
>        12        1       1        0        1   taunew(  12)=(  0.2703  0.1207  0.1069)
>        13        1       1        0        1   taunew(  13)=(  0.0915  0.2816  0.1069)
>        14        1       1        0        1   taunew(  14)=( -0.0312  0.2944  0.1069)
>        15        1       1        0        1   taunew(  15)=( -0.2395  0.1740  0.1069)
>        16        1       1        0        1   taunew(  16)=( -0.2896  0.0613  0.1069)
>        17        1       1        0        1   taunew(  17)=( -0.2395 -0.1740  0.1069)
>        18        1       1        0        1   taunew(  18)=( -0.1478 -0.2565  0.1069)
>        19        1       1        0        1   taunew(  19)=(  0.0915 -0.2816  0.1069)
>        20        1       1        0        1   taunew(  20)=(  0.1983 -0.2198  0.1069)
>        21        1       1        0        1   taunew(  21)=(  0.2395  0.1740  0.2138)
>        22        1       1        0        1   taunew(  22)=(  0.1478  0.2565  0.2138)
>        23        1       1        0        1   taunew(  23)=( -0.0915  0.2816  0.2138)
>        24        1       1        0        1   taunew(  24)=( -0.1983  0.2198  0.2138)
>        25        1       1        0        1   taunew(  25)=( -0.2960  0.0000  0.2138)
>        26        1       1        0        1   taunew(  26)=( -0.2703 -0.1207  0.2138)
>        27        1       1        0        1   taunew(  27)=( -0.0915 -0.2816  0.2138)
>        28        1       1        0        1   taunew(  28)=(  0.0312 -0.2944  0.2138)
>        29        1       1        0        1   taunew(  29)=(  0.2395 -0.1740  0.2138)
>        30        1       1        0        1   taunew(  30)=(  0.2896 -0.0613  0.2138)
>     k slab    z(k)  z(k+1)     crossing(iorb=1,norb)
>     1   0.0000 0.0079 0.0079   111111111100000000000000000000
>     2   0.0079 0.0158 0.0079   111111111100000000000000000000
>     3   0.0158 0.0238 0.0079   111111111100000000000000000000
>     4   0.0238 0.0317 0.0079   111111111100000000000000000000
>     5   0.0317 0.0396 0.0079   111111111100000000000000000000
>     6   0.0396 0.0475 0.0079   111111111100000000000000000000
>     7   0.0475 0.0554 0.0079   111111111111111111110000000000
>     8   0.0554 0.0633 0.0079   111111111111111111110000000000
>     9   0.0633 0.0713 0.0079   000000000011111111110000000000
>    10   0.0713 0.0792 0.0079   000000000011111111110000000000
>    11   0.0792 0.0871 0.0079   000000000011111111110000000000
>    12   0.0871 0.0950 0.0079   000000000011111111110000000000
>    13   0.0950 0.1029 0.0079   000000000011111111110000000000
>    14   0.1029 0.1108 0.0079   000000000011111111110000000000
>    15   0.1108 0.1188 0.0079   000000000011111111110000000000
>    16   0.1188 0.1267 0.0079   000000000011111111110000000000
>    17   0.1267 0.1346 0.0079   000000000011111111110000000000
>    18   0.1346 0.1425 0.0079   000000000011111111110000000000
>    19   0.1425 0.1504 0.0079   000000000011111111110000000000
>    20   0.1504 0.1583 0.0079   000000000011111111111111111111
>    21   0.1583 0.1663 0.0079   000000000011111111111111111111
>    22   0.1663 0.1742 0.0079   000000000000000000001111111111
>    23   0.1742 0.1821 0.0079   000000000000000000001111111111
>    24   0.1821 0.1900 0.0079   000000000000000000001111111111
>    25   0.1900 0.1979 0.0079   000000000000000000001111111111
>    26   0.1979 0.2058 0.0079   000000000000000000001111111111
>    27   0.2058 0.2138 0.0079   000000000000000000001111111111
> 
>         k(    1) = (   0.0000000   0.0000000), wk =   1.0000000
> 
>  ngper, shell number =         2809         299
> ####################################################################################
> the output file stopped  there, and I couldn't see the process. Maybe it takes long time cause I found it took 1 hour to calculate a transmission.
> I don't quite understand the parameters setting, I have adjusted the ewind, epsproj, nzl, according to the postings on this forum. However, 
> the result seemed not change. 
> 
> I appreciate everyone who could give me some advice.
> Thank you!
> 
> Regards.
> 
> Chengyu Yang
> Material Science and Engineering,
>  University of Central Florida, USA
> 
> 
>      
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne







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