[CP2K:6529] Re: Only CELL_OPT with the given structure of the molecule

[arobendo mondal]

Thank you Florian.

I am new to CP2K and have never played with these keywords. I was looking 
into regtest files but didn't get anything reasonable for this purpose. 
Could you please help me with the input file.

Best wishes
Arobendo


On Tuesday, 5 May 2015 23:17:04 UTC+2, Florian Schiffmann wrote:
>
> Hi,
>
> I haven't cheged the output file, but in general there is a problem 
> defining what fixed means if you change scale your coordinate system 
> (cell). The famous example of painting two dots on a ballon and blowing it 
> up. The dots do not move but their distance increases as the coordinate 
> systems (surface of the baloon expands). The motion of atoms you see should 
> only be in absolute cartesians but not in fractional coordinates (which is 
> the only meaningful way to fix them). 
> If you want a given absolute distance preserved you will have to specify a 
> COLVAR (e.g. distance) in TOPOLOGY, and then use it in the CONSTRAINT 
> section with the RESTRAINT section set and a reasonably large K to add a 
> spring term which drives your system in the desired state. 
> However be careful. The Total energy now contains the contribution from 
> the spring and is thus an artificial energy. If you want to compare 
> energies in that case you will have to look at the SCF energies.
>
> Cheers
> Flo 
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20150507/5c7f778a/attachment.htm>