[Pw_forum] ibrav=2 and space_group=202: input coordinate misunderstood
Musil Félix
felix.musil at epfl.ch
Fri Sep 15 22:22:04 CEST 2017
Dear Paolo,
I am not sure to understand. The documentation on ibrav=2 shows the following cell convention:
2 cubic F (fcc)
v1 = (a/2)(-1,0,1), v2 = (a/2)(0,1,1), v3 = (a/2)(-1,1,0)
which corresponds to a fcc primitive cell and the position input that I provide corresponds to this cell.
How could the position input be in simple cubic while the cell input is a primitive cell ?
Thanks for your prompt reply.
Cheers,
Felix
Félix Musil
Doctoral Assistant - Ph.D Student
EPFL STI IMX COSMO
LABORATORY OF COMPUTATIONAL SCIENCE AND MODELLING
Institute of Materials Science and Engineering
MXG 319
Station 12
CH-1015 Lausanne
Switzerland
E-mail: felix.musil at epfl.ch
http://cosmo.epfl.ch/
________________________________
De : pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> de la part de Paolo Giannozzi <p.giannozzi at gmail.com>
Envoyé : vendredi 15 septembre 2017 21:31
À : PWSCF Forum
Objet : Re: [Pw_forum] ibrav=2 and space_group=202: input coordinate misunderstood
If I remember correctly Wyckoff positions for fcc crystals are in simple cubic axis (the so-called "conventional" unit cell), while the atom you are looking at in the output is in crystal axis of the fcc cell. If you look at the same atom in cartesian axis:
1 Si tau( 1) = ( -0.6943213 0.4949861 0.5050079 )
it has the same x,y,z positions as the input one, displaced by (1.5, 0.0, 0.5)
Paolo
On Fri, Sep 15, 2017 at 6:52 PM, Musil Félix <felix.musil at epfl.ch<mailto:felix.musil at epfl.ch>> wrote:
Dear QE developers,
I am running the following input file and the resulting output has changed the non equivalent scaled atomic coordinates (see highlighted in yellow). I compared with space group 224 with ibrav=1 and these scaled coordinates do match. Is there a reason for this particular behavior ?
Please find attached an input file to reproduce this behavior.
Cheers,
Felix Musil
QE INPUT:
&CONTROL
calculation = "scf"
outdir = "./out/"
prefix = "qe"
pseudo_dir = "/scratch/musil/run_qe/pseudo/SSSP_acc_PBE/"
restart_mode = "from_scratch"
verbosity = "high"
wf_collect = .false.
/
&SYSTEM
ecutrho = 40.00000
ecutwfc = 10.00000
ibrav = 2
nat = 1
nbnd = 57
ntyp = 1
occupations = "smearing"
smearing = "cold"
degauss = 0.010000
space_group = 202
A = 11.740480817708141
/
&ELECTRONS
conv_thr = 0.10000000
/
ATOMIC_SPECIES
Si 28.0855 Si.pbe-n-rrkjus_psl.1.0.0.UPF
ATOMIC_POSITIONS crystal_sg
Si 0.80567873 0.49498614 0.00500792
QE OUTPUT:
Program PWSCF v.6.1 (svn rev. 13369) starts on 15Sep2017 at 18:33: 4
This program is part of the open-source Quantum ESPRESSO suite
for quantum simulation of materials; please cite
"P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
URL http://www.quantum-espresso.org",
in publications or presentations arising from this work. More details at
http://www.quantum-espresso.org/quote
Parallel version (MPI), running on 8 processors
R & G space division: proc/nbgrp/npool/nimage = 8
Reading input from /scratch/musil/data/check_input_errors/sg_202-f_0-0/qe.in<http://qe.in>
.
.
.
celldm(1)= 22.186293 celldm(2)= 0.000000 celldm(3)= 0.000000
celldm(4)= 0.000000 celldm(5)= 0.000000 celldm(6)= 0.000000
crystal axes: (cart. coord. in units of alat)
a(1) = ( -0.500000 0.000000 0.500000 )
a(2) = ( 0.000000 0.500000 0.500000 )
a(3) = ( -0.500000 0.500000 0.000000 )
.
.
.
Crystallographic axes
site n. atom positions (cryst. coord.)
1 Si tau( 1) = ( 0.7043430 0.3056728 0.6842995 )
2 Si tau( 2) = ( 0.3056728 0.7043430 0.3056847 )
3 Si tau( 3) = ( 0.3056847 0.6842995 0.3056728 )
4 Si tau( 4) = ( 0.6842995 0.3056847 0.7043430 )
5 Si tau( 5) = ( 0.6842995 0.3056728 0.3056847 )
6 Si tau( 6) = ( 0.3056847 0.7043431 0.6842995 )
7 Si tau( 7) = ( 0.3056728 0.6842995 0.7043431 )
8 Si tau( 8) = ( 0.7043431 0.3056847 0.3056728 )
9 Si tau( 9) = ( 0.3056847 0.3056728 0.7043430 )
10 Si tau( 10) = ( 0.6842995 0.7043430 0.3056728 )
11 Si tau( 11) = ( 0.7043430 0.6842995 0.3056847 )
12 Si tau( 12) = ( 0.3056728 0.3056847 0.6842995 )
13 Si tau( 13) = ( 0.2956570 0.6943272 0.3157005 )
14 Si tau( 14) = ( 0.6943272 0.2956570 0.6943153 )
15 Si tau( 15) = ( 0.6943153 0.3157005 0.6943272 )
16 Si tau( 16) = ( 0.3157005 0.6943153 0.2956570 )
17 Si tau( 17) = ( 0.3157005 0.6943272 0.6943153 )
18 Si tau( 18) = ( 0.6943153 0.2956569 0.3157005 )
19 Si tau( 19) = ( 0.6943272 0.3157005 0.2956569 )
20 Si tau( 20) = ( 0.2956569 0.6943153 0.6943272 )
21 Si tau( 21) = ( 0.6943153 0.6943272 0.2956570 )
22 Si tau( 22) = ( 0.3157005 0.2956570 0.6943272 )
23 Si tau( 23) = ( 0.2956570 0.3157005 0.6943153 )
24 Si tau( 24) = ( 0.6943272 0.6943153 0.3157005 )
Félix Musil
Doctoral Assistant - Ph.D Student
EPFL STI IMX COSMO
LABORATORY OF COMPUTATIONAL SCIENCE AND MODELLING
Institute of Materials Science and Engineering
MXG 319
Station 12
CH-1015 Lausanne
Switzerland
E-mail: felix.musil at epfl.ch<mailto:felix.musil at epfl.ch>
http://cosmo.epfl.ch/
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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