[QE-users] Units for {crystal_b} Configuration

[Stephen Zhang]

Thank you Pietro, this has been very helpful

On Sat, Jul 11, 2020 at 12:06 PM Pietro Delugas <pdelugas at sissa.it> wrote:
>
> Dear Stephen Zhang
>
> crystal_b for positions is meaningless, it is used only for specifying
> K-POINTS  paths in band structure calculations, that's why the program
> gets confused and uses Bohrs.
>
> Please have a look to the documentation here
>
> https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm1064
>
> for the possible modes to write atomic positions in the input
>
> best wishes
>
> Pietro
>
>
>
> On 11/07/20 20:42, Stephen Zhang wrote:
> > Hi Everyone,
> >
> > I am currently running relaxation computations with quantum Espresso,
> > and I am unsure what the units are for the {crystal_b} configuration
> > when determining the positions of the atoms, below is my input. I am
> > assuming that celldm(1) is in angstrom, however on xcrysden, it says
> > that these units are in Bohr. Can anyone provide some clarification on
> > this?
> > Thanks
> >
> > &control
> >      calculation = 'vc-relax'
> >      prefix = 'CoSnS'
> >      outdir = './outdir'
> >      pseudo_dir = '/home/stephen/qe-6.5/SSSP_precision_pseudos'
> >      etot_conv_thr = 1e-5
> >      forc_conv_thr = 1e-4
> > /
> > &system
> >      ibrav=5, celldm(1) =5.381186316302011, celldm(4) = 0.4980629252775897,
> >      nat=7, ntyp=3,
> >      ecutwfc=70
> >      occupations='smearing',smearing='gaussian',degauss=0.01
> > /
> > &electrons
> >      conv_thr=1e-8
> > /
> > &ions
> > /
> > &cell
> >      cell_dofree='ibrav'
> > /
> > ATOMIC_SPECIES
> >   Co  58.933195 Co.pbe-spn-kjpaw_psl.0.3.1.UPF
> >   Sn  118.71 Sn.pbe-dn-kjpaw_psl.1.0.0.UPF
> >   S  32.065 S.pbe-n-kjpaw_psl.1.0.0.UPF
> > ATOMIC_POSITIONS {crystal_b}
> >   Co 0.5000 0.0000 0.0000
> >   Co 0.0000 0.5000 0.0000
> >   Co 0.0000 0.0000 0.5000
> >   Sn 0.5000 0.5000 0.5000
> >   Sn 0.0000 0.0000 0.0000
> >   S 0.7195 0.7195 0.7195
> >   S 0.2805 0.2805 0.2805
> > K_POINTS (automatic)
> >    4 4 4 0 0 0
> >
> >
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University of California, Berkeley
Department of Letter and Sciences