[Pw_forum] Irreps and vibrational modes

Paolo Giannozzi giannozz at democritos.it
Mon May 14 17:35:26 CEST 2012

On Mon, 2012-05-14 at 03:07 +0100, Elie M wrote:

> (1) Are all the modes vibrational?

there are always three translational modes

> (2) Are any modes missing from the calculation

there shouldn't be anything missing

> (3) i did the calculation and got two of the modes negative

if they go to zero when you apply the acoustic sum rule, with all
other modes unchanged or litle affected, it is not a problem


Paolo Giannozzi, IOM-Democritos and University of Udine, Italy

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