Static calculation with Selective dynamics switched on.

[Danny]

Hi,

I just did a test in which in one case I used the selective Dynamics tag in the POSCAR file, and all boolean tags for the atoms set to F and IBRION= -1 in INCAR,
and in the second case none of these tags were used. As far as I understood from the manual these 2 settings should do exactly the same calculations? The results proved me wrong so I would like to know what the actual difference is and how this influences calculations.

Code: Select all

[b]with tags[/b]
       N       E                     dE             d eps       ncg     rms          rms(c)
DAV:   1     0.174654125930E+05    0.17465E+05   -0.42067E+05 10048   0.316E+03
DAV:   2     0.338912000284E+04   -0.14076E+05   -0.13692E+05 11496   0.697E+02
DAV:   3    -0.471437747708E+02   -0.34363E+04   -0.32410E+04 12868   0.215E+02
DAV:   4    -0.459677061969E+03   -0.41253E+03   -0.40119E+03 11632   0.857E+01
DAV:   5    -0.479483658228E+03   -0.19807E+02   -0.19605E+02 11840   0.208E+01    0.343E-01
DAV:   6    -0.480132764528E+03   -0.64911E+00   -0.75340E+00 13760   0.377E+00    0.151E-01
DAV:   7    -0.480153683630E+03   -0.20919E-01   -0.21949E-01 11112   0.110E+00    0.117E-01
DAV:   8    -0.480155607902E+03   -0.19243E-02   -0.21888E-02 11864   0.494E-01    0.962E-02
DAV:   9    -0.480156217919E+03   -0.61002E-03   -0.69205E-03 16928   0.183E-01    0.839E-02
DAV:  10    -0.480156150872E+03    0.67047E-04   -0.25162E-04 11376   0.497E-02    0.617E-02
DAV:  11    -0.480156113019E+03    0.37853E-04   -0.64565E-05 10536   0.400E-02    0.449E-02
DAV:  12    -0.480156083479E+03    0.29540E-04   -0.46879E-05  9992   0.297E-02    0.250E-02
DAV:  13    -0.480156072754E+03    0.10725E-04   -0.30236E-05  7808   0.214E-02    0.800E-03
DAV:  14    -0.480156072956E+03   -0.20221E-06   -0.12223E-05  5920   0.136E-02
   1 F= -.48015607E+03 E0= -.48015494E+03  d E =-.338462E-02


[b]without tags[/b]

       N       E                     dE             d eps       ncg     rms          rms(c)
DAV:   1     0.174675717427E+05    0.17468E+05   -0.42085E+05 10048   0.316E+03
DAV:   2     0.339579315384E+04   -0.14072E+05   -0.13688E+05 11496   0.697E+02
DAV:   3    -0.438717723215E+02   -0.34397E+04   -0.32391E+04 12836   0.215E+02
DAV:   4    -0.459180731439E+03   -0.41531E+03   -0.40389E+03 11544   0.858E+01
DAV:   5    -0.479509910141E+03   -0.20329E+02   -0.20116E+02 12024   0.210E+01    0.326E-01
DAV:   6    -0.480132389542E+03   -0.62248E+00   -0.72641E+00 13728   0.368E+00    0.145E-01
DAV:   7    -0.480153696815E+03   -0.21307E-01   -0.22245E-01 11160   0.112E+00    0.113E-01
DAV:   8    -0.480155563524E+03   -0.18667E-02   -0.21164E-02 11816   0.490E-01    0.913E-02
DAV:   9    -0.480156197975E+03   -0.63445E-03   -0.70551E-03 16952   0.182E-01    0.803E-02
DAV:  10    -0.480156139428E+03    0.58547E-04   -0.24310E-04 11216   0.494E-02    0.588E-02
DAV:  11    -0.480156104145E+03    0.35283E-04   -0.63353E-05 10520   0.396E-02    0.413E-02
DAV:  12    -0.480156081217E+03    0.22929E-04   -0.40323E-05  9184   0.286E-02    0.233E-02
DAV:  13    -0.480156072678E+03    0.85385E-05   -0.27295E-05  7336   0.213E-02
   1 F= -.48015607E+03 E0= -.48015494E+03  d E =-.338346E-02

Thx Danny,
<span class='smallblacktext'>[ Edited ]</span>

[admin]

the calculations converge to the same total energies up to the last digit, (both F and E0), so they ae equivalent. As VASP starts form a random wavefunction, the history of electronic relaxation may differ for 2 runs.