[Pw_forum] phonon dispersion calculations

Paolo Giannozzi giannozz at nest.sns.it
Tue Aug 8 22:55:54 CEST 2006

On Tuesday 08 August 2006 13:37, Tuhina Kelkar wrote:

> I want [...] to calculate the phonon dispersion for MgH2 along the 
> following high symmetry points: Gamma to X to M to Gamma to Z
> to R to A to Z. But I am not being able to construct the matdyn.in file.
> How does one decide on the number of q-points?  

it depends on what you want to do with them. If you just want nice
dispersions, you need as many q-points as needed for a nice plot

> And how to go about creating this list of q-points to be used in matdyn.in?

one after the other, in units of 2pi/a

> I have already obtained the IFC's and the following is the resulting q2r.out
> file: 
> reading grid info from file dyn0
>   reading force constants from file dyn1
>   Dielectric Tensor not found

and thus no LO-TO splitting. You need epsil=.true. in the
input of the phonon calculation at q=0

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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