[Pw_forum] a question on 4-phonons interactions

[Stefano Baroni]

On Jul 30, 2008, at 12:34 PM, L.F.Huang (黄良锋) wrote:

> Dear Prof. Baroni:
>  According to the linear response theory and 2n+1 theorem
> (Rev.Mod.Phys.73,515),
> it seems that PWSCF can not calculate 4-phonons interactions. But in  
> effect,
> the process of 4-phonons interactions is as important as 3-phonons
> interactions.

sometimes

> Then my question is:
>  Is there any approach to calculate the anharmonicity of some  
> vibration
>  modes including 4-phonons interactions ?

I do not see any other way than frozen phonons or, maybe, a  
combination of frozen phonons with perturbation theory. I have never  
thought in depth at what an optimal strategy can be, but Alberto  
Debernardi has (see, e.g. Alberto Debernardi, Manuel Cardona, First  
principles calculation of the real part of phonon self energy in  
compound semiconductors, Physica B: Condensed MatterVolumes 263-264, ,  
March 1999, Pages 687-690). You may want to contact Alberto: his e- 
mail address is: alberto.debernardi at mdm.infm.it

regards - SB

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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