[Pw_forum] phonon calculations in a spercell of 100 atoms
Paolo Giannozzi
giannozz at democritos.it
Mon Feb 13 21:45:09 CET 2012
On Feb 13, 2012, at 16:41 , Lorenzo Paulatto wrote:
> If you only need the phonons at the gamma point, it may be faster
> to get them by finite displacement, doing 3*nat pw.x ground state
> calculations.
faster? not sure, and not by much anyway. A phonon calculation at q=0
also
requires 3*nat self-consistent linear-response calculations. Each
such calculation
has a computational cost comparable to that of a self-consistency.
Usually one
needs to perform two finite-difference calculations with opposite
displacements
in order to get good numerical accuracy, by the way. Or at least,
this is the way
I would do it.
For q=0 phonons, using k=0 only for the Brillouiin zone sampling, and
norm-conserving
PP, there is the simplified version of the phonon code that is
definitely faster and takes
(relatively) little memory
P.
---
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
More information about the users
mailing list