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

[Jon Halverson]

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
>
> _______________________________________________
> ESPResSo mailing list
> address@hidden
> https://fias.uni-frankfurt.de/mailman/listinfo/espresso