Re: [ESPResSo] pressure tensor cannot be calculated for cossquare

[Mikhail Stukan]

Jon,

Thanks a lot!
Although this bug looks a bit strange, since as far as I can
understand, it means that if I tabulate my cossquare potential then
everything should be fine. Do you know if there are plans to fix this
problem in the nearest future?

Thanks and regards,
Mikhail

On Sun, Apr 4, 2010 at 3:58 PM, Jon Halverson
<address@hidden> wrote:
> Mikhail,
>
> yes, for the three-body potentials only the cossquare doesn't properly
> compute the pressure tensor (it ignores the off-diagonal elements).
> Everything is fine for cosine, harmonic and tabular.
>
> You can prove this to yourself by running a simulation with only three
> particles for a single time step and comparing the ESPResSo result to a
> calculation by hand. We've done this as well as much more extensive testing
> using a second simulation code and everything is consistent. This doesn't
> work for the cossquared potential simply because no one has done the coding
> for it yet (to do it just follow the examples of the others).
>
> Jon
>
>
> Mikhail Stukan wrote:
>>
>> Dear all,
>>
>> In  v2.1.5 vesion the is now a warning that pressure tensor cannot be
>> calculated for cossquare. Is this problem related to cossquare angle
>> potential only? If yes, then does it mean that in case of tabulated
>> angle potential there is no problem with pressure tensor calculation?
>>
>> Many thanks,
>> Mikhail
>>
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>