[Pw_forum] Construction of PtH structure, wrong pointgroup problem

Tue May 22 20:54:55 CEST 2012

```Hi,
I have a problem in constructing the PtH structure.
I have prepared the input with following data from J. Phys. Chem. C,
2012, 116 (2), pp 1995--2000
(http://http://pubs.acs.org/doi/abs/10.1021%2Fjp210780m) for hexagonal PtH.

Spacegroup : 194 - P63/mmc
Point group : D_6h
a=2.795
c=7.769
Pt: 2c (1/3 2/3 0.25)
H: 2a ( 0 0 0 )

Point group of this input  gives  D_3d (-3m) instead of D_6h (6/mmm). I
am not sure what am i missing.

here is my input for vc-relax under 100GPa (Espresso-4.3.2):

&CONTROL
calculation =   "vc-relax"   ,
restart_mode = 'from_scratch' ,
outdir='/tmp' ,
pseudo_dir ='/home/pseudos/espresso/' ,
etot_conv_thr = 1.0D-14  ,
forc_conv_thr = 1.0D-5 ,
prefix='PtH_sp194_100GPa.opt',
tstress=.true.,
verbosity='high'
/
&SYSTEM
ibrav= 4,
celldm(1)=5.2817842823,
celldm(3)=1.706261153,
nat= 4,
ntyp= 2,
ecutwfc=37
ecutrho  =  222 ,
occupations  =  'smearing' ,
smearing  =  'mp' ,
degauss  =  0.02 ,
/
&ELECTRONS
conv_thr  =  1.0d-7,
diagonalization='david'
/
&IONS
ion_dynamics = 'bfgs',
/
&CELL
cell_dynamics = 'bfgs' ,
cell_factor=1.2,
press= 1000.00
/

ATOMIC_SPECIES
Pt  195.08 Pt.pbe-n-van.UPF
H  1.00794 H.pbe-van_ak.UPF

ATOMIC_POSITIONS (crystal)
Pt       0.333333343   0.666666687   0.250000438
Pt       0.666666627   0.333333313   0.749999562
H        0.000000000   0.000000000   0.000000000
H        0.000000000   0.000000000   0.500000000

K_POINTS automatic
4 4 4 1 1 1

Thanks,