Stefano de Gironcoli
degironc at sissa.it
Wed May 11 14:13:09 CEST 2011
are you imposing acoustic sum rule ? this change slightly the frequencies .
isn't strange that your frequencies are all negative (imaginary) ?
is your system stable ?
05/11/2011 01:20 PM, S. K. S. wrote:
> Dear All,
> I find a bit strange results when using matdyn.x to perform the
> interpolation in order
> to get a complete phonon dispersion plot.
> In case of my system, at Gamma point, ph.x prints out two noticeably
> distinguishable triply degenerate phonon modes of frequency values as follows :
> -18.9595 -18.9595 -18.9595 -11.8835 -11.8835 -11.8835
> However, after using "matdyn.x" the above phonons become like :
> -18.6356 -18.6356 -18.6356 -18.6096 -18.6096 -18.6096
> This looks quite strange to me. As far as I understand, the phonon
> interpolation should
> not change the frequency values at Gamma point or any other
> high-symmetry point
> (suppose X in my case) which have been already computed by the
> QE_phonon code. Interpolation means, it should only generate more
> frequencies in between
> Gamma and X point, not changing the frequency values in the exact
> Gamma and X point, which have been already printed by the ph.x run.
> Looking forward to your comments.
> Thanking you and with my best regards,
> Saha S. K.
> R&D Assistant,
> Bangalore -560064
> Pw_forum mailing list
> Pw_forum at pwscf.org
More information about the users