comparing energies of finite clusters in boxes of different size

Matt W MattWa... at
Wed Nov 2 15:53:15 CET 2016


above a certain box size for a given system the energy should be 
essentially constant for the isolated system. There may be some noise if 
you change the box size if your cutoff is not sufficiently large.

If you are paranoid (careful) you could rerun smaller systems in your 
largest cell and check that the energies are consistent (note you can 
restart from wfn files whilst changing the box, so this shouldn't be very 


On Tuesday, November 1, 2016 at 10:24:14 PM UTC, Megha Anand wrote:
> Dear CP2K friends,
> Is it correct to obtain relative energy from the energies of optimized 
> structures in boxes of different size?
> I am doing non-periodic computations on finite clusters of different 
> stoichiometry using MT poisson solver. My box sizes is therefore different 
> for each structure. How do I get their relative energy?
> Even though these are non-periodic computations, isn't the energy affected 
> by the box size. What is the usual practice and recommendation.
> Thanks in advance for taking time to read and answer my question.
> Best regards,
> Megha
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