[Pw_forum] Atomic positions for Black Phosphorus calculations
Elio Physics
Elio-Physics at live.com
Mon Jan 11 23:44:50 CET 2016
Dear all,
I am trying to perform some calculations on Black Phosphorus (BP). To get the atomic positions I used the Crystal Builder, where I have chosen the lattice type to be base centered orthorhombic. The "builder" produced a set of cartesian and fractional (in terms of the primitive cell vectors) . I have used the fractional ones and I have also used ibrav=0 with the CELL_PARAMETERS defined as in the builder (a/2, -b/2, 0), (a/2, b/2,0), (0,0,c). However I have got the following error:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
from check_atoms : error # 1
atoms # 1 and # 4 overlap!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Doing the same calculation with ibrav=8 and using the coordinates produced by the Crystal builder for a simple orthorhombic does not produce any errors. Can anyone please tell me what is wrong with atoms (1) and (4). Is BP simple or base centered orthorhombic..Where can I find the coorect atomic position of bulk BP? The scf input is below:
&CONTROL
prefix='bp',
calculation='scf',
restart_mode='from_scratch',
wf_collect=.true.,
forc_conv_thr=1.D-4
etot_conv_thr=1.D-5
tstress=.true.,
tprnfor=.true.,
pseudo_dir ='/home_cluster/fis718/elio/espresso-4.1.3/pseudo',
outdir='/home_cluster/fis718/elio/espresso-4.1.3/BP/OUT'
/
&SYSTEM
ibrav=0,celldm(1)=6.26179,nat=8, ntyp= 1, ecutwfc=10, ecutrho=40, occupations='smearing', london=.true., smearing='mp', degauss=0.035,nbnd=32
/
&ELECTRONS
conv_thr=1.D-8,
mixing_beta=0.1
/
&IONS
ion_dynamics='bfgs'
/
&CELL
cell_dynamics='bfgs'
press=0.0
/
ATOMIC_SPECIES
P 30.97376 P.pbe-n-van.UPF
ATOMIC_POSITIONS crystal
P -0.89832 0.89832 0.91944
P -0.39832 0.39832 0.58056
P -0.10168 0.10168 0.08056
P 0.10168 0.89832 0.91944
P -0.10168 1.10168 0.08056
P -0.60168 0.60168 0.41944
P -0.39832 1.39832 0.58056
P 0.39832 0.60168 0.41944
K_POINTS automatic
2 2 2 0 0 0
CELL_PARAMETERS alat
0.5000 -1.58106 0.0000
0.500 1.58106 0.0000
0.0000 0.00000 4.3763
thanks
Elio Arbid
University of Nottingham
UK
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