[Pw_forum] Questions on how to define unit cell

[Stefano de Gironcoli]

celldm(1) is in unit of bohr radii not angstrom .
stefano


张 洪彬 wrote:

> Hello everyone:
> I am a beginner of PWSCF and now I am tortured by the very first step
> when I want to do some calculation of mine--I really don't know how to
> define a unit cell and whether what I have create is right or wrong.
> In the structure I used in my the file below,atoms' relative location
> is right but distances between them(read form XCrySDen) are not what I
> want though I have set to, for example, celldm(1)=3.0851 angs.
> Plz someone tell me how to make it.Or take graphite as an example to
> show me how to built the unit cell. Here is my input file for scf
> calculation of MgB2: &CONTROL
> calculation = 'scf' ,
> restart_mode = 'from_scratch' ,
> outdir = '/pwscf/tmp/' ,
> pseudo_dir = '/pwscf/pseudo/' ,
> prefix = 'mgb' ,
> /
> &SYSTEM
> ibrav = 4,
> celldm(1) = 3.0851,
> celldm(3) = 1.14100,
> nat = 3,
> ntyp = 2,
> ecutwfc = 18.0 ,
> /
> &ELECTRONS
> conv_thr = 1.0d-8 ,
> mixing_beta = 0.7 ,
> /
> ATOMIC_SPECIES
> Mg 24.30500 Mg.pz-bhs.UPF B 10.81100 B.pz-bhs.UPF ATOMIC_POSITIONS
> alat Mg 0.000000000 0.000000000 0.000000000 B 0.500000000 0.288680000
> 0.570500000 B 0.000000000 0.577350000 0.570500000 K_POINTS gamma
>
>
> Regars
>
> zhb
>
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