[Pw_forum] pwscf version 4.3 example 15 error

[Paolo Giannozzi]

On Jun 19, 2011, at 10:44 , xu yuehua wrote:

> my  results of example 15 has a liittle difference in alas.ph.out.
> i think it can not be neglected??

the difference between "true" frequencies is very small. The non-zero
value for the acoustic frequency is a well-known and hard to solve
problem. Those number vary a lot from machine to machine and
from version to version, but as long as they are small and disappear
by applying the Acoustic Sum Rule, they are not a problem

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