[Pw_forum] phonon frequencies with pwscf and cpmd

Paolo Giannozzi giannozz at nest.sns.it
Wed Mar 24 17:29:05 CET 2004

On Wednesday 24 March 2004 14:37, Massimiliano Bonomi wrote:

> My real question is if everyone can explain me 

are you sure you want explanations from "everyone" ?!?

> why this two codes give such different results in this particular
> calculation

- verify the atomic masses. Remember that "atomic units" means
  something different in cpmd and in pwscf !
- try simpler systems first: for instance, the normal mode of a sodium 
  dimer; a zone-boundary phonon of fcc Na

> Can it be due to the use of two different pseudopotentials?

such a large difference seems unlikely (unless one of the two PP
is bad, of course)

Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
Piazza dei Cavalieri 7      I-56126 Pisa, Italy

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