[Pw_forum] about neb

[Cyrille Barreteau]

dear Rongqin

Obviously doing a calculation with fictious substrate masses will lead
to a totally different system which has nothing to do with your
original system. However one could imagine calculating local spectral
density of states that would allow you to extract the contribution
of your molecule from the total spectrum. If the coupling with your
substrate is small this contribution will be rather well separated
from the substrate spectrum...

   good luck

     cyrille


Stefano Baroni wrote:
> In this way you will not obtain the normal modes of the physical system 
> you are interested in, but those of a fictitious system with different 
> masses. frequencies will be different, displacement patterns will be 
> different.
> The fact that you cannot disentangle exactly the modes in which the 
> adsorbed molecule vibrates from those in which the substrate atoms 
> vibrate is not an artifact of the calculation, but a fact of nature you 
> have to leave with (at least if you are interested in the way Nature 
> behaves rather than just in the output of a computer simulation).
> 
> best wishes,
> SB
> 
> On Jun 9, 2004, at 11:27 AM, Wu Rongqin wrote:
> 
>      
> 
>      Dear Dr. Baroni,
> 
>      
> 
>     I have thought of another way to calculate the norm mode of small
>     molecular absorbed on a surface.
> 
>     The idea is quite simple. Since the frequency is related closely to
>     the mass, then in the input file, I can set the mass of atoms in the
>     slab to a very large value so that the correspondent frequencies are
>     greatly lowered so the norm mode of small molecular absorbed can be
>     figured out.
> 
>     Just give me some comments on this and how to give a zero point
>     energy correlation
> 
>      
> 
>     Regards
> 
>      
> 
>     Rongqin
> 
>      
> 
> ---
> Stefano Baroni --- SISSA & DEMOCRITOS National Simulation Center
> via Beirut 2-4 34014 Trieste Grignano / [+39] 040 3787 406 (tel) -528 
> (fax)
> 
> 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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