[Pw_forum] Re:about the displacive instabilities

[Stefano Baroni]

On Jun 15, 2007, at 3:20 AM, li yan wrote:

> Dear Stefano
>      I'm so sorry and giving my delayed thanks to you,
>      I am not sure if i can continue the discussion of my previous  
> question. I have read the papers you suggested. And the authors  
> proposed that the softening mode coupled with the lattice strain  
> can induced a second or a slightly first order pahse transition.  
> But I stil have doubts in the displacive instabilitis.
>    The character of the  transition from NaCl to CsCl is thougt to  
> be  first order in experiment. May I cosider this  transition to be  
> induced by the lattice instability if I found the softening mode in  
> the  NaCl phase at the pressure which is consitent with the  
> experiment?

which normal-mode displacement would bring the NaCl structure to  
CsCl? what would be the order parameter of the transition?

S.

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
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