[Pw_forum] Comments on Graphene on BN relaxation
Ngoc Linh Nguyen
nnlinh at sissa.it
Tue Jan 26 18:02:09 CET 2010
> When I plot the graph, it looks like ecutwfc =60 is optimal. Is it
right? Is it the right way to do > it? Is the final energy (obtained
from last relaxation step) the right quantity?
I think what you did for checking E vs. ecutwfc is right. However, with
the big model it could be quite expensive. You can do like that: you
choose an ecutwfc value firstly, for example ecutwfc = 40 Ry, and relax
your model with that value, then increase the value ecutwcf and run scf
only, you can obtain a relation E vs. ecutwfc in similar.
> For Final energy (obtained from last relaxation step) vs d interlayer
distance at cutoff ecutwfc = 50.0:
> .... ecutwfc = 60.0
I am confusing about increasing of d values in your models.
If you keep the sizes of supercell unchanged, when increasing the
value of d, the 3rd layer of the above supercell and 1st layer of the
below supercell should be approached too close together, i.e. , let try
visualizing by Xcryden at different values of d. And it can reduce an
increase of energy of your models as d is lager.
Good luck,
Linh
mohamed sabri majdoub wrote:
> Dear all,
>
> I run calculations of 1 layer of graphene on bilyaer boron nitride.
> I am trying to study the Energy vs cutoff and Energy vs interlayer
> distance d between the graphene layer and top of BN layer.
> I got the following results after several runs. Is it the right way to
> do it?
> Here is the input file I am using:
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> &control
> title = 'GphBN'
> calculation = 'relax'
> outdir = '/pwscf/pwscftemp'
> prefix = 'GphBN'
> pseudo_dir = '/pseudopot-C-B-N'
> tprnfor = .t.
> restart_mode = 'from_scratch'
> wf_collect = .true.
> disk_io = 'low'
> /
> &system
> ibrav = 0,
> celldm(1) = 1.8897261
> nat = 72,
> ntyp = 3,
> ecutwfc = 60.0
> occupations = 'smearing'
> smearing = 'gaussian'
> degauss = 0.003675
>
> /
> &electrons
> mixing_mode = 'local-TF'
> mixing_beta = 0.05
> diagonalization = 'david'
> conv_thr = 1.D-5
> /
> &ions
> trust_radius_ini = 0.10
>
> /
> &cell
>
> ATOMIC_SPECIES
> B 10.81100 B.pz-vbc.UPF
> C 12.01070 C.pz-vbc.UPF
> N 14.00674 N.pz-vbc.UPF
> ATOMIC_POSITIONS angstrom
> B 0.710000 8.607000 11.306000
> B 0.710000 11.066000 11.306000
> B 2.840000 7.377000 11.306000
> B 0.710000 6.148000 11.306000
> B 6.390000 6.148000 8.000000
> B 6.390000 8.607000 8.000000
> B 6.390000 11.066000 8.000000
> B 2.840000 9.836000 11.306000
> B 7.100000 7.377000 11.306000
> B 7.100000 9.836000 11.306000
> B 7.100000 12.295000 11.306000
> B 4.970000 11.066000 11.306000
> B 2.840000 12.295000 11.306000
> B 4.970000 6.148000 11.306000
> B 4.970000 8.607000 11.306000
> B 4.260000 7.377000 8.000000
> B 2.130000 11.066000 8.000000
> B 2.130000 8.607000 8.000000
> B 2.130000 6.148000 8.000000
> B 4.260000 9.836000 8.000000
> B 0.000000 7.377000 8.000000
> B 0.000000 9.836000 8.000000
> B 4.260000 12.295000 8.000000
> B 0.000000 12.295000 8.000000
> C 2.130000 6.148000 14.106000
> C 2.130000 8.607000 14.106000
> C 2.130000 11.066000 14.106000
> C 0.000000 12.295000 14.106000
> C 0.000000 9.836000 14.106000
> C 0.000000 7.377000 14.106000
> C 0.710000 11.066000 14.106000
> C 0.710000 8.607000 14.106000
> C 0.710000 6.148000 14.106000
> C 6.390000 8.607000 14.106000
> C 6.390000 6.148000 14.106000
> C 4.970000 11.066000 14.106000
> C 6.390000 11.066000 14.106000
> C 7.100000 12.295000 14.106000
> C 7.100000 9.836000 14.106000
> C 7.100000 7.377000 14.106000
> C 4.970000 8.607000 14.106000
> C 2.840000 12.295000 14.106000
> C 2.840000 9.836000 14.106000
> C 2.840000 7.377000 14.106000
> C 4.260000 7.377000 14.106000
> C 4.970000 6.148000 14.106000
> C 4.260000 12.295000 14.106000
> C 4.260000 9.836000 14.106000
> N 0.000000 12.295000 11.306000
> N 0.000000 9.836000 11.306000
> N 0.000000 7.377000 11.306000
> N 2.840000 7.377000 8.000000
> N 2.840000 9.836000 8.000000
> N 2.840000 12.295000 8.000000
> N 4.970000 11.066000 8.000000
> N 4.970000 8.607000 8.000000
> N 4.970000 6.148000 8.000000
> N 7.100000 12.295000 8.000000
> N 7.100000 9.836000 8.000000
> N 7.100000 7.377000 8.000000
> N 0.710000 6.148000 8.000000
> N 0.710000 8.607000 8.000000
> N 0.710000 11.066000 8.000000
> N 6.390000 11.066000 11.306000
> N 6.390000 8.607000 11.306000
> N 6.390000 6.148000 11.306000
> N 2.130000 11.066000 11.306000
> N 2.130000 8.607000 11.306000
> N 2.130000 6.148000 11.306000
> N 4.260000 12.295000 11.306000
> N 4.260000 9.836000 11.306000
> N 4.260000 7.377000 11.306000
> K_POINTS automatic
> 10 10 1 1 1 0
> CELL_PARAMETERS
> 8.51980 0.00000 0.00000
> 0.00000 7.37600 0.00000
> 0.00000 0.00000 22.6120
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> The results are :
>
> 1- Final energy (obtained from last relaxation step) vs cutoff (ecutwfc)
>
> cut20: Final energy = -857.6291985882 Ry
> cut30: Final energy = -876.5012327526 Ry
> cut40: Final energy = -885.4765196610 Ry
> cut50: Final energy = -890.0493283821 Ry
> cut60: Final energy = -892.0114549785 Ry
> cut70: Final energy = -892.8706506804 Ry
> cut80: Final energy = -893.2520149989 Ry
>
> When I plot the graph, it looks like ecutwfc =60 is optimal. Is it
> right? Is it the right way to do it? Is the final energy (obtained
> from last relaxation step) the right quantity?
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------
> 2- For Final energy (obtained from last relaxation step) vs d
> interlayer distance at cutoff ecutwfc = 60.0:
>
> d=2.5= Final energy = -892.0122348924 Ry
> d=3.0= Final energy = -892.0119194861 Ry
> d=3.1= Final energy = -892.0089055437 Ry
> d=3.2= Final energy = -892.0104083862 Ry
> d=3.3= Final energy = -892.0115677649 Ry
> d=3.4= Final energy = -892.0113018510 Ry
> d=3.5= Final energy = -892.0121118001 Ry
> d=3.6= Final energy = -892.0113544429 Ry
> d=3.7= Final energy = -892.0096184164 Ry
> d=3.9= Final energy = -892.0041914533 Ry
>
> There are fluctuations in the data? Is it normal?
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>
> 3- For Final energy (obtained from last relaxation step) vs d
> interlayer distance at cutoff ecutwfc = 50.0:
>
> d=2.5= Final energy = -890.0504214490 Ry
> d=2.8= Final energy = -890.0503533642 Ry
> d=2.9= Final energy = -890.0503471460 Ry
> d=3.0= Final energy = -890.0486572147 Ry
> d=3.1= Final energy = -890.0491375298 Ry
> d=3.2= Final energy = -890.0480863744 Ry
> d=3.3= Final energy = -890.0492074574 Ry
> d=3.4= Final energy = -890.0501303488 Ry
> d=3.6= Final energy = -890.0488317041 Ry
> d=3.5= Final energy = -890.0492797825 Ry
> d=3.7= Final energy = -890.0470527582 Ry
> d=3.8= Final energy = -890.0443250729 Ry
> d=3.9= Final energy = -890.0412177248 Ry
>
> Same thing for these data.
> Is there any thing wrong?
> Your suggestions are welcomed.
>
> Thank you in advance for your help!
>
> Regards,
>
> ME
> University of Houston
>
>
>
>
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