[Pw_forum] ASR

[Stefano Baroni]

On Dec 25, 2008, at 5:30 PM, Reza Ebraahimi wrote:

> Hi

Hi

> can anyone refer me to some literature about history of acoustic sum  
> rules? i mean when was it proposed for the first time?

Pick, Cohen, Martin, Phys. Rev. B 1, 910 - 920 (1970)

> and it's versions known here as "simple" and "crystal"?

"simple" only deals with q->0 frequencies, and modifies the q=0  
dynamical matrix so as to impose that the sum of the eigenvalues  
vanishes (this can be achieved by subtracting T/N from the diagonal  
elements, where T is the trace and N the dimension); "crystal" would  
do something more sophisticated on the interatomic force constants, so  
as to enforce continuity in the q->0 limit. do not know if the details  
have ever been written anywhere

> Thank You

you are most welcome. you would be even more so if you took the time  
of signing your posts to this forum, including your accademic  
affiliation.

Best wishes

Stefano Baroni

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
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http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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