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["zhangtingPKU" <zhangting@pku.edu.cn>]

Dear all

            I'm interested in the phonon-phonon interaction problem, like the 
Umklapp process. To handle such a process like an optic phonon spliting into 
two acoustic phonons with ab-initio method, we need the 3rd order expansion 
of the potential:

         U3= (1/6)sigma(B*R1*R2*R3)

        And in particular, the 3rd order anharmonic coefficients are the most 
important. I've read the paper "Density-functional approach to 
nonlinear-response coefficients of solids" (PRB 39,13120, Year 1989), and I'm 
interested in whether the ABINIT code can perform such a third-order 
coefficients calculation. This kind of task is not included in the tutorials, 
and I have made some attempt but it failed. Can someone tell me how can I 
perform this calculation? Thanks!
        In attachment are my test files and the error message in log file. I 
don't clearly know what's the meaning of the keywords like "rf2phon" and 
"rf3phon". Does this mean the third phonon or the 3rd order perturbation?


　　　　　　　　致
礼！
                                

　　　　　　　　zhangtingPKU
　　　　　　　　zhangting@pku.edu.cn
　　　　　　　　　　2006-08-04

Attachment: 3phonon.in
Description: Binary data

Attachment: log.txt
Description: Binary data