[Pw_forum] Problem with lattice optimization

[Mojtaba Mirseraji]

Dear

You have to optimize Kpoints and ecuts
After you can find the correct lattice constants

Regards
Mojtaba Mirseraji
Arak univ.
Iran

On 11/9/16, sayan chaudhuri <csayan895 at gmail.com> wrote:
> Dear All,
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>  I am trying to optimize the lattice parameter of Fe2TiSb by running the
> following code self consistently. But somehow it is giving a lattice
> parameter of 6.82 Angstrom, which is nowhere near to the lattice parameter
> I am getting experimentally ( 6.017 Angstrom).
> My input file is the following,
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> * &CONTROL                 calculation = 'scf' ,
> restart_mode = 'from_scratch' ,                  wf_collect = .true.
> ,                      pseudo_dir = './',
> outdir='./'                      prefix = 'fta' ,
> verbosity = 'low' ,                     tstress = .false.
> ,                     tprnfor = .false. , / &SYSTEM
> ibrav = 2,                   celldm(1) =12.92,                         nat
> = 4,                        ntyp = 3,                     ecutwfc = 60.0
> ,                     ecutrho = 250.0 ,                        nbnd =
> 30,                 occupations = 'smearing' ,                     degauss
> = 0.002 ,                    smearing = 'marzari-vanderbilt'
> ,                       nspin = 2 ,   starting_magnetization(1) = 0.5,
> starting_magnetization(2) = 0.6,   starting_magnetization(3) =
> 0.5, / &ELECTRONS            electron_maxstep = 200,
> conv_thr = 1e-8 ,                 mixing_mode = 'plain' ,
> mixing_beta = 0.3 ,             diagonalization = 'david'
> , /ATOMIC_SPECIES   Fe   55.84500  Fe.pbe-mt_fhi.UPF    Ti   47.86700
> Ti.pbe-mt_fhi.UPF    Sb  121.76000  Sb.pbe-mt_fhi.UPF ATOMIC_POSITIONS
> Fe      0.250000000    0.250000000    0.250000000       Fe
> 0.750000000    0.750000000    0.750000000       Sb      0.000000000
> 0.000000000    0.000000000       Ti      0.500000000    0.500000000
> 0.500000000    K_POINTS {automatic}   2 2 2   0 0 0 *
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> Where I am changing the celldm(1) in each run.
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> Please tell me what am I doing wrong in the calculation.
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>  Thanking you in advance,
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>                Sayan Chaudhuri
>                IIT Indore
>