[CPMD-list] the difference between isolated molecule and Cell

[Christian Tuma]

Dear Rongjian,

as far as I know the keyword "ISOLATED MOLECULE" is important for a normal
mode analysis of a molecule. Here you have 3 (2) degrees of freedom which 
correspond to rotations of the molecule (eigenvalues close to zero). In
periodic systems they correspond to internal degrees of freedom (eigenvalues
not zero). That's all I guess ... maybe you can make such a "VIBRATIONAL
ANALYSIS" with and without the keyword "ISOLATED MOLECULE" to see the
difference ...

Good luck,
Christian.


On Tue, Nov 26, 2002 at 10:34:13AM +0800, Rongjian Sa wrote:
> Dear everyone,
> 
> I want to know what is the difference if the isolated molecule option was selected? I have compared the optimized results and total energy of some molecule, I can not find any difference when use this option or not use. So who can tell me when and how I can use it ?
> Thank you!
> Sincerely yours,
> Rongjian Sa
-- 
Christian Tuma             Humboldt-Universitaet Berlin
ct at chemie.hu-berlin.de     Arbeitsgruppe Quantenchemie (Prof. Sauer)
phone: +49-30-20937140     Brook-Taylor-Str. 2, 12489 Berlin, GERMANY
fax:   +49-30-20937136     http://www.chemie.hu-berlin.de/ag_sauer