[Pw_forum] Graphene structure

[Gabriele Sclauzero]

Ti has an open d shell in valence. Why don't you treat the system as metallic (i.e. use smearing)? Moreover you might need to take into account spin-polarization as well (nspin=2).

HTH

GS

Il giorno 22/nov/2010, alle ore 13.47, Ettore Baldini Neto ha scritto:

> Dear QE users,
> 
> I'm kinda new with quantum espresso. I'm trying to relax a Graphene structure with  32C atoms plus one Ti atom at a given position and the structure do not converge.
> In what follows I copy the input. Could anyone give-me some hint? Is there anything wrong or that can be improved? I'm using the pp's from the QE data base. I'm planning to generate my own pp's soon.
> I'm using a k-point grid of 6x6x1 since with SIESTA (dzp basis) the energy and force convergence is achieved without problem.
> 
> With best regards,
> 
> ************************************************************
> Dr. Ettore Baldini-Neto
> Wernher von Braun Center for Advanced Research
> Campinas, Brazil.
> ************************************************************
> 
> &CONTROL
>  title = 'Graphene mono layer'
>  calculation =   "relax"   ,
>  restart_mode = 'from_scratch' ,
>  outdir='/home/usuarios/baldini/espresso-4.2.1/tmp/' ,
>  pseudo_dir = '/home/usuarios/baldini/espresso-4.2.1/pseudo' ,
>              etot_conv_thr = 1.0E-4  ,
>              forc_conv_thr = 1.0D-3 ,
>              nstep=50,
>              dt=40,
>              prefix='1MLG_Ti_H2',
> /
> &SYSTEM
>                      ibrav = 0.,
>                      ntyp = 2 ,
>                      nat = 33 ,
>                      ecutwfc = 50.0 ,
>                      ecutrho = 400.0,
> /
> &ELECTRONS
>            electron_maxstep = 300.,
>            conv_thr  =  1.0d-8  ,
>            mixing_mode = 'plain',
>            mixing_beta = 0.5,
>            diagonalization   =   'cg' ,
>            diago_cg_maxiter = 50,
> /
> &IONS
> /
> CELL_PARAMETERS
> 16.12131954   9.383047808   0.0000000
> 0.00000000  18.658162370   0.0000000
> 0.0000000    0.0000000    56.6893424
> ATOMIC_SPECIES
> C   12.0107   C.pbe-van_ak.UPF
> Ti  47.8670   Ti.pbe-sp-van_ak.UPF
> ATOMIC_POSITIONS angstrom
> C      2.89163        7.40219        1.8862
> C      3.59292        8.63832        1.8826
> C      3.60349        6.16702        1.8884
> C      5.0186         8.64501        1.8612
> C      5.0215         6.16598        1.8904
> C      5.73302        7.40522        1.8718
> C      1.47184        7.39616        1.891
> C      2.89112        9.87066        1.886
> C      2.89471        4.93264        1.8916
> C      5.73319        9.8885         1.8612
> C      5.73643        4.9413         1.8924
> C      7.16348        7.41203        1.882
> C      1.47474        4.9269         1.8924
> C      0.762281       8.62783        1.8946
> C      0.763134       6.16172        1.8914
> C      1.4715         9.86335        1.8934
> C      3.60341        11.1095        1.8868
> C      5.02124        11.1239        1.882
> C      3.60512        3.70156        1.8932
> C      5.02645        3.70789        1.891
> C      7.87807        8.65532        1.8816
> C      7.16373        9.89497        1.872
> C      7.16203        4.94814        1.8954
> C      7.87619        6.17677        1.8996
> C      5.73634        12.3522        1.8872
> C      0.772689       3.69102        1.898
> C      0.762793       1.22003        1.8968
> C      7.87645        11.1337        1.8894
> C      7.16203        12.3587        1.889
> C      7.87201        13.5922        1.8942
> C      2.89479        2.46619        1.8922
> C      1.47482        2.45878        1.8952
> Ti     6.41604        8.65974        3.74
> K_POINTS {automatic} 
> 6.0 6.0 1.0 1.0 1.0 1.0
> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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