[Pw_forum] IFC's and eigendisplacements in example06

Stefano Baroni baroni at sissa.it
Thu Dec 13 16:47:50 CET 2007

Dear Ömer:

> 1) Could you give me some analysis and explanations on the range of  
> the interatomic force constants (IFC's) for AlAs in example06.
>  On the Forum, there are  some informations and explanations but i  
> don't understand them. I need more explanations.

ask a question and we will try to answer. "give me some explanations"  
is not a question. We could give many explanations to problems that  
you do not have, so we would waste my time. In the lack of any hints  
on what your problem is, the best advice I can give you is to study  
some classical textbooks on lattice dynamics (such as Born and Huang)

>  2) Is there a meaning of ratio of displacement of the two ions (Al  
> and As) in the eigendisplacement pattern?

the meaning is that they are normal modes in the sense that is  
explained in the "small vibrations" chapter of any classical mechanics  
textbook (such as, e.g. Landau or Goldstein)

> The calculated vibrational eigenvectors at X point are below. How  
> can we evaluate this data?

what do you want to evaluate?


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

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html

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