[Pw_forum] Re: [Pw_forum] Re: [Pw_forum] »Ø¸´£º Re: [Pw_forum] negtive values for TA when using q2r.x

[Katalin Gaal-Nagy]

Hi Eyvaz,

thanks for the answer!

> I just suggested that an unstable mode near Gamma
> point might be a result of incorrectly determined
> dynamical matrix (and then unstable mode) at X point,
> and consequently, force constants obtained by q2r.x
> are also not correct.  I am not sure that you will be
> able to get correct behavior of the phonon spectrum
> (obtained using matdyn.x) with wrong interatomic force
> constants. Are not you agree with this?

Of course, I agree with this. I just assumed that the unstable mode at X 
is correct and the error is just close to Gamma, which can be quite 
reasonable (it was like this in my case). But of course, I was overlooking 
that it could be seen also in the opposite way.

Best wishes,
Katalin