Re: [ESPResSo-devel] Pressure calculation / P3M stress tensor

[Axel Arnold]

Am Freitag 03 April 2009 15:13 schrieb Kai Grass:
> Hi,
>
> can someone tell me if the warning issued by the pressure calculation
> that the P3M stress tensor is not implemented (pressure.c, line 176)
> is obsolete? There definitely is some code in that section ...

No, the warning is not obsolete. The stress _tensor_ is not calculated. What 
that routine does, is distributing the isotropic pressure onto the trace of 
the pressure, rather than really calculating the stress tensor. Therefore, 
only the _isotropic_ pressure calculated from the tensorial one is correct.
Implementing the stress tensor for P3M would be quite a bit of work, and as 
far as I remember, involves a _lot_ of Fourier transforms.

Axel

-- 
Dr. Axel Arnold 
Fraunhofer SCAI
Schloss Birlinghoven, 53754 Sankt Augustin, Germany
Tel: +49 2241 14 2575