[QE-users] Units for {crystal_b} Configuration

[Pietro Delugas]

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
>
>