[Pw_forum] Silent Calculations
S. K. S.
sks.jnc at gmail.com
Sat Aug 9 08:30:13 CEST 2008
On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:
> Only for Gamma point phonon one can use "Frozen
> phonon" method because it is much faster.
not true in general. Each linear-response calculation
costs approx. as much as a self-consistent one, and
you need at least as many scf calculations as
linear-response calculations.
Dear Sir,
I agree with you that for small system each
linear-response calculation
costs approx. as much as a self-consistent one, and
we need at least as many scf calculations as
linear-response calculations.
However, IN CASE OF very large system (say about 64 atoms per unit cell),
I found that a single representation takes too much computer time
compared to a single scf run.
Moreover, in some cluster which have multiple cpu
for each node and in some quad or octa core computer, always
phonon paralization is much slower than manual
scf paralization (I mean manually divide your all scf calculations in
different processors). In case of Frozen phonon method, one can
also accomplish the same goal by using less memory and
disk space.
However, for non-zone center phonon Linear response is the best way.
There is still a scope in PWSCF to make Phonon calculation much faster
by implementing the representation number parallization.
regards,
SKS
JNCASR
BANGALORE
On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:
>
> On Aug 8, 2008, at 18:41 , S. K. S. wrote:
>
> > Only for Gamma point phonon one can use "Frozen
> > phonon" method because it is much faster.
>
> not true in general. Each linear-response calculation
> costs approx. as much as a self-consistent one, and
> you need at least as many scf calculations as
> linear-response calculations
>
> Paolo
> ---
> Paolo Giannozzi, Dept of Physics, University of Udine
> via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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