ISIF: Difference between revisions

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For {{TAG|ISIF}}=1, only the trace of the stress tensor is calculated. This means only the total pressure is correctly written to the {{FILE|OUTCAR}} file. See the line:
external pressure =      ... kB


== Related Tags and Sections ==
== Related Tags and Sections ==

Revision as of 12:25, 9 April 2014

ISIF = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 

Default: ISIF = 0 for IBRION=0 (molecular dynamics)
= 2 else

Description: ISIF determines whether the stress tensor is calculated and which principal degrees-of-freedom are allowed to change in relaxation and molecular dynamics runs.


ISIF determines whether the stress tensor is calculated. The calculation of the stress tensor is relatively time-consuming, and therefore by default switched off for ab initio molecular dynamics runs. The forces are always calculated.

In addition ISIF determines which degrees-of-freedom (ionic positions, cell volume, and cell shape) are allowed to change.

The following table shows all combinations:

ISIF calculate degrees-of-freedom
forces Stress tensor positions cell shape cell volume
0 yes no yes no no
1 yes trace only yes no no
2 yes yes yes no no
3 yes yes yes yes yes
4 yes yes yes yes no
5 yes yes no yes no
6 yes yes no yes yes
7 yes yes no no yes

For ISIF=1, only the trace of the stress tensor is calculated. This means only the total pressure is correctly written to the OUTCAR file. See the line:

external pressure =      ... kB


Related Tags and Sections

IBRION, ISIF, LEPSILON, LCALCEPS


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