[Pw_forum] Negative Phonon Dispersion after geometry optimization twice.

Mohammed Ghadiyali m786g at live.co.uk
Wed Sep 7 13:12:06 CEST 2016

Thanks for the Reply.

The negative frequencies are not just at gamma but along the axis of k vector (please check attachment for phonon dispersion png)

>> If somewhere else, you have a phase instability and a soft phonon mode 
>>(if it's a charge density wave, not evident say GGA will be good enough)

Was not able to get what did you meant?  As for the literature almost all work on the 2D tin has been done using VASP.
Can you inform me what general procedure you do recommend for the geometry optimization and relax.
I am using phononpy for the phonon dispersion calculation as I was not able to get documentation regarding q2r.x and matdyn.x  

Ghadiyali Mohammed Kader. 		 	   		  
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