[Pw_forum] Comments on Graphene on BN relaxation

mohamed sabri majdoub majdoub at gmail.com
Tue Jan 26 17:22:20 CET 2010


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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