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QuantumATK => General Questions and Answers => Topic started by: bubble on May 2, 2017, 05:50

Title: Soft model in pnonon spectra
Post by: bubble on May 2, 2017, 05:50

Dear all,
I have two questions.
First, for phonon spectra, we found some negative frequencies. I want to know whether the negative frequencies in solid can be called as soft model , i.e., negative frequencies and soft models  have the same meanings in solid?
( It is well known that negative frequencies in molecules or clusters are usually used to indicate transtion states)

Second, through the "VibrationalMode", can we obtain the specific vibration of a negative frequency?

Thank you very much for your reply.

Title: Re: Soft model in pnonon spectra
Post by: Daniele Stradi on May 2, 2017, 08:40

Hi,

Soft phonon modes are not necessary negative, but they might become under certain conditions, indicating a phase-transition.

I think that with VibrationalMode you should be able to obtain the eigenmode even if it has a negative frequency.

Regards,
Daniele.