[CPMD-list] How can one estimate the error of calculated energy ?

[Axel Kohlmeyer]

On Nov 11, 2007 8:17 PM, liu liuxiandong <xiandongliu at gmail.com> wrote:
>
> Dear CPMD users,
>
>   How can I estimate the error of the energy value of single-point calculation ?
>  For example, I got an energy difference of about 20 kJ/mol of >  two different configurations. How can I evaluate the energy
> difference: is it significant or negligible ?

you can determine this by using common sense.
you can compare the energy differece to that of
a single C-C bond or to the typical thermal energy
in your system per degree of freedom (derived from kT).

but since you didn't tell us how your configurations are
different, nobody can tell you whether 20kJ is a lot or little.

> In the manual, I cannot find the evaluation from the topic "What accuracy
> can I expect?". Thanks for your suggestion.

if you read the manual more carefully, you'd have noticed
that this section applies to the calculation of NMR shifts only.

axel.

>
> BEST,
>
> Xiandong Liu
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>



-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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