[Pw_forum] about the displacive instabilities

[Stefano Baroni]

Hi, Li Yan. This is a good question which, I am sure, has been  
addressed many times in many places. There are for sure a number of  
textbook references. The only one that occurs to me by heart is  
unfortunately in French [N. Boccara, Symmetries brisees (Hermann,  
Paris, 1976)]. Any textbook dealing with Landau's theory of phase  
transitions would do. The literature in the field looks often more  
complicated than it actually should. You may want to take a glance at  
a pair of old papers of mine where your issue is addressed using  
minimum theoretical background.

NARDELLI MB, BARONI S, GIANNOZZI P
HIGH-PRESSURE LOW-SYMMETRY PHASES OF CESIUM-HALIDES
PHYSICAL REVIEW B 51 (13): 8060-8068 APR 1 1995

NARDELLI MB, BARONI S, GIANNOZZI P
PHONON SOFTENING AND HIGH-PRESSURE LOW-SYMMETRY PHASES OF CESIUM IODIDE
PHYSICAL REVIEW LETTERS 69 (7): 1069-1072 AUG 17 1992

Hope you will find something useful in them. If not, I will try to  
write a short explanation, but for this you will have to wait for me  
to find 1-2 hours of spare time, which is not going to be tomorrow ...

Cheers - Stefano


On Jan 9, 2007, at 8:54 AM, li yan wrote:

> Dear all,
>       Since the displacive phase transition is second order, why  
> some first order transitions are considered to be induced by the  
> displacive instabilities? would you please give me some advices or  
> some reference papers about this?
>                                                                        
>               best regards
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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