[Pw_forum] about ph.x calculation on system with symmetry

[feng zhu]

Dear All,

I want to do phonon calculation on an adsorption system with symmetry. So I
did some test calculations below.

I did a test calculation on a system, say H2O in the cubic cell, with
ph.xand only gamma point (both in scf and phonon ).
At first, I calculated all the representations. Then ph.x calculated 3*3=9
representations (9 SCF calcuclation).
But why not calculated only 6 representations because of the symmetry?

Then I set nat_todo=1 and let only the first H atom to move. But the program
calculated both two H atoms, and 6 representations (for 2 H ) are
calculated.
Why not only calculated only the first 3 representations of the first
H? (nrapp can be used to fix the representations to be done, this may be a
resolution for this problem?)

Thank you for your reply in advance!

Yours,
zhu
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