[Pw_forum] Is the Graphite surface flate?

[Giuseppe Mattioli]

Dear Masoud
apart from the pseudo problem issued by Andrea, you could try the keyword
london=.true.
It adds a Van der Waals contribution to total energy and it is likely to 
improve the interlayer interactions in your system.
Hope this helps
Giuseppe 
 
On Monday 05 July 2010 20:19:19 Masoud Nahali wrote:
> Dear Quantum Espresso users
>
> I optimized the graphite bulk and the
>  layers were completely flat. But when I try to "relax" the graphite
> surface (slab 2*2 with 3 monolayer) with 10 angstrom vacuum all the layers
> become extremely ripple!!! I can not find the problem. May it related to
> the number of layers? anyhow the number of layers is like the bulk. Your
> help would be a great gift.
>
> input file:
>
> &CONTROL
>
> calculation  = "relax",
>   pseudo_dir   =
> "/home/koa/soft/qe4.2/espresso-4.2/pseudo",
>   outdir       =
> "/home/koa/tmp",
>   etot_conv_thr= 1.0D-4,
>   forc_conv_thr= 1.0D-3,
>
>  nstep=150,
>   /
> &SYSTEM
>   ibrav     = 4,
>   a         =
> 4.9318,
>   b         = 4.9318,
>   c         = 16.7029,
>
> cosab     = -0.5,
>   cosac     = 1.0,
>   cosbc     = 1.0,
>
> nat       = 24,
>   ntyp      = 1,
>   ecutwfc   = 40.D0,
>
> ecutrho   = 400.D0,
>   occupations = 'smearing'
>   smearing ='mp',
>
>  degauss = 0.01,
>   nspin = 2,
>   starting_magnetization(1)= 1.0,
>
>  /
> &ELECTRONS
>   conv_thr    = 1.D-6,
>   mixing_beta = 0.7D0,
>
>  diagonalization = "david",
> /
> &IONS
>  ion_dynamics="bfgs"
> /
> ATOMIC_SPECIES
> C
>  12.0107  C.star1s-pbe-rrkjus.UPF
> ATOMIC_POSITIONS {angstrom}
> C
>  0.000000    0.000000    0.000000
> C    2.465900    0.000000
> 0.000000
> C    -1.232950    2.135532    0.000000
> C    1.232950
> 2.135532    0.000000
> C    0.000000    1.423688    0.000000
> C
> -1.232950    3.559220    0.000000
> C    2.465900    1.423688
> 0.000000
> C    1.232950    3.559220    0.000000
> C    0.000000
> 0.000000    3.351450
> C    2.465900    0.000000    3.351450
> C
> -1.232950    2.135532    3.351450
> C    1.232950    2.135532
> 3.351450
> C    1.232950    0.711844    3.351450
> C    0.000000
> 2.847376    3.351450
> C    3.698850    0.711844    3.351450
> C
> 2.465900    2.847376    3.351450
> C    0.000000    0.000000
> 6.702900
> C    2.465900    0.000000    6.702900
> C    -1.232950
> 2.135532    6.702900
> C    1.232950    2.135532    6.702900
> C
> 0.000000    1.423688    6.702900
> C    -1.232950    3.559220
> 6.702900
> C    2.465900    1.423688    6.702900
> C    1.232950
> 3.559220    6.702900
> K_POINTS {automatic}
> 4 4 1 1 1 1
>
>
> out
>  put (optimized positions):
>
> C        0.000000000
> -0.000000000  -0.686394528
> C        2.465900000  -0.003714144
> -0.758610095
> C       -1.229733457   2.137389072  -0.758610095
> C
>  1.229733457   2.137389072  -0.758610095
> C        0.000000000
> 1.427474855  -0.213813075
> C       -1.229670488   3.557326573
> -0.213813075
> C        2.465900000   1.423688000  -0.285079086
> C
>  1.229670488   3.557326573  -0.213813075
> C       -0.000000000
> 0.000000000   3.630366631
> C        2.465900000  -0.014904710
> 3.544792504
> C       -1.220042143   2.142984355   3.544792504
> C
>  1.220042143   2.142984355   3.544792504
> C        1.220249305
> 0.704511250   3.106073641
> C        0.000000000   2.847376000
> 3.022325711
> C        3.711550695   0.704511250   3.106073641
> C
>  2.465900000   2.862041499   3.106073641
> C        0.000000000
> 0.000000000   7.468882932
> C        2.465900000   0.008344370
> 7.466151214
> C       -1.240176436   2.131359815   7.466151214
> C
>  1.240176436   2.131359815   7.466151214
> C        0.000000000
> 1.414904155   6.963129179
> C       -1.240557033   3.563611923
> 6.963129179
> C        2.465900000   1.423688000   6.961528237
> C
>  1.240557033   3.563611923   6.963129179
>
>
>
> Many Thanks
> Masoud Nahali
> Sharif
>  University of Technology
>
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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
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