[Pw_forum] decomoposition of the atomic contribution to the vibrational spectrum

[Konstantin Kudin]

 Dear Li,

 As with most non-standard requests, you got to be prepared to work for
it :-)

 Anyway, I think this kind of analysis is known as "potential energy
distribution" (PED), and was reasonably popular for molecules in the
old days.

 There is a program that did the PED with the Gaussian vibrational
output, it is here:
http://www.ccl.net/cca/software/SOURCES/FORTRAN/gar2ped/index.shtml

 That should give you a starting point, naturally, you will still have
to deal with formats, add 3 degrees of freedom which are no longer
rotations for 3D periodic systems, and define a bunch of internal
coordinates which would be messy in the case of the 3D interconnected
carbon. Even if do not actually need the PED, the program still has
most of the components you are looking for.

 So go ahead and please report back on your success!

 Good luck!
 Kostya

--- li niu <niuli1978 at yahoo.com.cn> wrote:

> Dear all,
>   I onced asked this problem but could still not solved it. My
> question
>   is about the projection of  vibrational spectrum. 
>  In order to further decompose the carbon contribution to the
> vibrational spectrum, as in the paper "Vibrational properties of
> trtrahedral amorphous carbon from first principles"[APL
> 75,644(1999)], we should define for each bond a "stretching" vector
> in the space of the 3N (N is the number of atoms) displacement. The
> components of each vector involves the displacement of two atoms in
> the direction of the bond and with opposite orientations. We use
> these vectors as a
>   (non-orthonormal) basis of the stretching subspace and define the
> bending
>   subspace as the complement of the stretching subspace.
>   My problems:
>   How can I construct the stretching subspace and orthorgonalize
> these
>   vectors in 3N space?
>  Which one code may I use?
>    
>   need your help, any help will be appreciated!
>   
>   best regards!
>   
>   Niu Li                        
>   Harbin Institue of Technology                     
>   People's Republic of China
>  
>  		
> ---------------------------------
>  Mp3·è¿ñËÑ-иèÈȸè¸ßËÙÏ   >
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