[Pw_forum] ecut dependence of symmetry operations(?)

[kyin.cn]

This maybe relate with FFT grid. Try to specify parameters 'nr' in inputfile. You can get the reference value by executing this command in outputfile of ecut =20,25,...
$grep 'FFT grid:' ***.out

Kun Yin, PhD student
Nanjing University, China
2010-01-05 



kyin.cn 



发件人： Madhura Marathe 
发送时间： 2010-01-05  12:37:30 
收件人： pw_forum 
抄送： 
主题： [Pw_forum] ecut dependence of symmetry operations(?) 
 
 Dear all,
 While performing convergence calculations w.r.t energy cut-off for a bulk
system, I found that the number of symmetry operations detected by a code
is different depending on the value of ecut. This is very surprising
because for the same system, the symmetries should not depend on the ecut
value.
 For Ecut = 20, 25, 40, 50 and 55 Ry, the output says -
"24 Sym.Ops. (with inversion)";
whereas for ecut = 30, 35, 45 and 60 Ry, the output is -
"12 Sym.Ops. (no inversion)"
 I have performed the same calculations using versions 4.0.4 and 4.1 with
the same results.
The input file is as follows -
*****
 &control
    calculation = 'scf'
    verbosity = 'high'
    restart_mode = 'from_scratch',
    prefix = 'RuGGA',
    tstress=.true.
    tprnfor=.true.
    pseudo_dir = '/home/madhura-data/pseudo/',
    outdir = '/home/madhura-data/tmp/'
/
 &system
    ibrav = 4, celldm(1) = 5.1831, celldm(3) = 1.584,
    nat = 2, ntyp = 1,
    ecutwfc = 20, ecutrho = 160,                     # ecutrho = 8*ecutwfc
    occupations='smearing', smearing='mp',degauss=0.05
    nbnd = 20
/
 &electrons
    diagonalization = 'david', mixing_mode = 'plain',
    mixing_beta = 0.7, conv_thr = 1.0d-12
/
ATOMIC_SPECIES
 Ru 101.07 Ru.pbe-n-van.UPF
ATOMIC_POSITIONS {crystal}
 Ru 0.00       0.00       0.00
 Ru 0.66666667 0.33333333 0.50
K_POINTS automatic
 8 8 8 0 0 0
*****
 Can anybody explain what is happening? Or do I need to file a bug report?
Because except for this problem, energies and stress values seem to be
converging.
 Thanks and regards,
 Madhura.
-- 
Madhura Marathe,
PhD student, TSU,
JNCASR, Bangalore.
India.
Phone No: +91-80-22082835
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