[Pw_forum] Comments on Graphene on BN relaxation

Ngoc Linh Nguyen nnlinh at sissa.it
Tue Jan 26 20:00:04 CET 2010


mohamed sabri majdoub wrote:
> Dear Linh,
>
> Thank you for your response.
> So, do you suggest that I should increase the supercell size (by the 
> same amount of d increase) each time I increase the value of d?
You should do that if d values change by moving 1st and 3rd layer and 
keep middle layer.
Somehow, let try to keep away the interactions of the layers between 
neighbor supercells.
> Thanks,
>
> On Tue, Jan 26, 2010 at 11:02 AM, Ngoc Linh Nguyen <nnlinh at sissa.it 
> <mailto:nnlinh at sissa.it>> wrote:
>
>      > 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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