[Pw_forum] Get wrong symmtry

[Axel Kohlmeyer]

On Sun, 9 Nov 2008, yumin qian wrote:

YQ> Dear Prof.
YQ> 
YQ>  I am doing LaOFeAs ground state calculation , it symmetry blongs to
YQ>   p4/nmm space group , when I finish the ground state calculation , I
YQ> procced to do the phonon calculation of Gamma point , But the output file
YQ> tell me that at Gamma point the symmetry is C_4v , but it should be D_4h,
YQ> then I look at the x.save fold to find the data-file.xml  I find the
YQ> symmetry operation is completely different from the D_4h , I also use the
YQ> Vasp to do the calculation and I get the D_4h symmetry operation , I check
YQ> the possible error of my in put file for SCF calculation the only possible
YQ> error is the parameter ibrav=6, and the crystal is indeed a
YQ> Tetragonal P (st)  cell
YQ>    where is the errror ? Or what mistake I have made , is there someone to

how about not having enough numerical accuracy 
for the numbers in the z-coordinate?

axel.

YQ> tell me what's the problem ? Thanks ,I am looking forward to the answer.
YQ> 
YQ> 
YQ> this is my input file for ground state SCF calculation
YQ> 
YQ> 
YQ>  &control
YQ>     calculation='scf'
YQ>     restart_mode='from_scratch',
YQ>     pseudo_dir = '~/software/espresso-4test/pseudo',
YQ>     outdir='./outscf'
YQ>     prefix='LaOFeAs',
YQ>     wf_collect=.true.
YQ>     tstress = .true.
YQ>     tprnfor = .true.
YQ>  /
YQ>  &system
YQ>     ibrav = 6, celldm(1) =7.633740 , celldm(3)=2.136,
YQ>     , nat= 8, ntyp= 4,
YQ>     ecutwfc = 30.0, ecutrho = 250.0
YQ>     occupations='smearing', smearing='gaussian', degauss=0.02,
YQ>  /
YQ>  &electrons
YQ>     diagonalization='david'
YQ>     conv_thr = 1.0e-10
YQ>     mixing_beta = 0.5
YQ>  /
YQ> ATOMIC_SPECIES
YQ> La  138.9 La.pbe-nsp-van.UPF
YQ> O   16.00 O.pbe-rrkjus.UPF
YQ> Fe  55.85 Fe.pbe-sp-van.UPF
YQ> As  74.92 As.pbe-n-van.UPF
YQ> ATOMIC_POSITIONS
YQ> La    0.2500000000    0.2500000000    0.1461000000
YQ> La    0.7500000000    0.7500000000    0.8539000000
YQ> O     0.7500000000    0.2500000000    0.0000000000
YQ> O     0.2500000000    0.7500000000    0.0000000000
YQ> Fe    0.7500000000    0.2500000000    0.5000000000
YQ> Fe    0.2500000000    0.7500000000    0.5000000000
YQ> As    0.2500000000    0.2500000000    0.6369000000
YQ> As    0.7500000000    0.7500000000    0.3631000000
YQ> K_POINTS (automatic)
YQ>  8 8 4 0 0 0
YQ> ~
YQ> 
YQ> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.