[Pw_forum] non-diagonalized stress on Chromium spinel

[Marino Vetuschi Zuccolini]

Hello to all,

I need to approach a study on chromium-spinel mineral and I would like  
to use a planewave code as pwscf. My experiences was only with  
localized atomic basis set and then the change of "language" is for me  
a source of questions.
My main question about the results of a run of the reported input file  
is:
- how can I detect the possible sources of errors or simply a bad  
description of system in the case as is, if the stress on the primitive  
cell is not diagonalized (that for me is a sign of structural  
unstability)?

This is the last one input file. In the previous I changed  
diagonalization, smearing, broadening, ecut*, number of k-points but  
nothing really has changed. Then vibrations are completely wrong..

Many thanks to all for any help,

marino

************************************************************************ 
****

  &CONTROL
                        title = 'Chromium spinel ICSD #75623' ,
                  calculation = 'scf' ,
                 restart_mode = 'restart' ,
                       outdir = '/tmp/' ,
                   wf_collect = .true.,
                   pseudo_dir = '/apps/espresso-2.1.3/pseudo/',
                       prefix = 'MgCrspinel' ,
                    verbosity = 'high' ,
                      disk_io = 'minimal',
                      tstress = .true.,
  /
  &SYSTEM
                        ibrav = 1,
                    celldm(1) = 15.75,
                          nat = 3,
                         ntyp = 3,
                      ecutwfc = 35 ,
                       ecutrho = 300 ,
                         nbnd = 20 ,
                        nspin = 2,
    starting_magnetization(2) = 0.2,
                  occupations = 'smearing' ,
                      degauss = 0.05 ,
                     smearing = 'm-v'
  /
  &ELECTRONS
             electron_maxstep = 200,
                  mixing_beta = 0.1,
              diagonalization = 'diis',
                 mixing_ndim = 3 /
ATOMIC_SPECIES
    Mg   24.30500  Mg.pw91-np-van.UPF
     Cr   51.99610  Cr.pw91-sp-van.UPF
      O   15.99940  O.pw91-van_ak.UPF
ATOMIC_POSITIONS crystal
Mg       0.125   0.125   0.125
Cr       0.500   0.500   0.500
O        0.2615  0.2615  0.2615
K_POINTS automatic
  4 4 4  1 1 1

************************** output *********************************
...
      npt with |zeta| > 1:    91168, npt tot   729000,    12.51 %

      npt with rhoup < 0:    14443, npt tot   729000,     1.98 %

      npt with rhodw < 0:   105467, npt tot   729000,    14.47 %
           total   stress  (ryd/bohr**3)                 (kbar)     P=   
-10.24
   -0.00006959  -0.00003860  -0.00003860        -10.24    -5.68     -5.68
   -0.00003860  -0.00006959  -0.00003860         -5.68   -10.24     -5.68
   -0.00003860  -0.00003860  -0.00006959         -5.68    -5.68    -10.24

      kinetic stress (kbar)   1319.27    -14.50    -14.50
                               -14.50   1319.27    -14.50
                               -14.50    -14.50   1319.27

      local   stress (kbar)  -3106.47  -1019.77  -1019.77
                             -1019.77  -3106.47  -1019.77
                             -1019.77  -1019.77  -3106.47

      nonloc. stress (kbar)    663.92      1.49      1.49
                                 1.49    663.92      1.49
                                 1.49      1.49    663.92

      hartree stress (kbar)   2283.49    458.71    458.71
                               458.71   2283.49    458.71
                               458.71    458.71   2283.49

      exc-cor stress (kbar)   -362.41      0.38      0.38
                                 0.38   -362.41      0.38
                                 0.38      0.38   -362.41

      corecor stress (kbar)   -114.70     -0.09     -0.09
                                -0.09   -114.70     -0.09
                                -0.09     -0.09   -114.70

      ewald   stress (kbar)   -693.32    568.11    568.11
                               568.11   -693.32    568.11
                               568.11    568.11   -693.32

      hubbard stress (kbar)      0.00      0.00      0.00
                                 0.00      0.00      0.00
                                 0.00      0.00      0.00



      Writing file MgCrspinel.sav for program phonon
       PWSCF        :     2h 4m CPU time


*******************************************************
Marino Vetuschi Zuccolini
zucco at dipteris.unige.it
PhD / Geochemist
Laboratory of Geochemistry
http://ugo.dipteris.unige.it/pesto

Visit our BAXEICO computing cluster homepage
http://qed.dipteris.unige.it/ganglia/?c=Baxeico%20Cluster

DIPartimento per lo studio della TErra e delle sue RISorse - Università  
  di Genova
Tel. ++39 010 3538136 Fax. ++39 010 352169
Corso Europa 26, 16132 - Genova - Italy
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