[Pw_forum] phonon calculation for optimized geometry -one subtle confusion

[Paolo Giannozzi]

On Apr 18, 2010, at 13:30 , mohnish pandey wrote:

> when I am doing scf calculation with the geometrical parameters
> value obtained from the vc-relax calculation the pressure value is
> different from vc-relax final run.

as explained a diverging number of times (even recently): the
plane-wave basis set used during variable-cell calculations is
determined by the given cutoff and the INITIAL cell. If you
make a calculation with the final geometry at the same cutoff,
you may get slightly different  results. The difference should
be small, though.

P.
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222