Ciao Giacomo,
On Mon, 10 Sep 2012, Giacomo Giorgi wrote:
...
I mean, as you mention, I have cheated Vibra just leaving in the .fdf file
the atoms whose frequencies I want to calculate, 44 as said.
...
Ok, but your Siesta FC calculation is for a block of 132 atoms,
correct ?.
So, have you also deleted in the *.FC file the lines corresponding
to atoms 45 and on ?. They are the last 88 of every block of 132 lines.
...
Let me take advantage of your kindness. Let me ask you one last question.
What about the
%block PolarizationGrids ?
...
Sorry, I've never used that. However, my understanding of it is that
it will not affect the energy, and thus the frequencies. Polarization
is a byproduct of the calculation, whose band contribution is given
by an integral in reciprocal space. Notice it only depends on the
fully periodic factor of the Bloch function, that's got a "k"
subscript. If you ask for different k's than present in the M&P grid,
probably they'll be interpolated (???).
Best,
Roberto
