[ESPResSo-users] Espresso modifications and more....

[Michael Winokur]

Hi Olaf,

Thanks for the quick reply.  Although it wouldn't be 
trivial it could be added.  Tinker has this coded in Fortran (which 
means I can almost cut'n'paste) and I could revise the Espresso dipole 
module to deal with both dipole and quadrupoles.  I'm not sure I want to
 deal with bound dipoles.

I also note that I've revised all my Gay-Berne modifications this 
summer to better deal with anisotropic particle rotational inertias.  I 
found and fixed some subtle mistakes but now the code appears to give 
the right physics using reported benzene  parameters with the thermostat
 on so that rotational and translational motion partition the kinetic energy 
evenly.  Would anyone be interested in these revisions?

Simple things still elude me though.  I'm not sure how to convert 
the time step into real time units.  Is there an easy way?  I'm also 
trying to make sense of the Van Hove correlation function results.  Thus one this on my wish lists, the configuration bias Monte Carlo module for short side chains,  is still a "to do" option.  
Simulation isn't as easy as it looks....

Thanks again,

Michael

On Sat, Aug 27, 2011 at 6:10 AM, Olaf Lenz <address@hidden> wrote:

In principle, I guess that one could extend the dipolar P3M-algorithm for point-like dipoles to point-like quadrupoles, but I would guess that the formulas would become pretty unwieldy. No, this is not implemented in ESPResSo, and it would not be trivial.
But of course you can set up quadrupoles by setting up four bonded charges close to each other, or two dipoles.
Does this anwer your question?
Olaf
--
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Michael Winokur <address@hidden> schrieb:

Hi,

I notice that Espresso has code for dealing with charge dipoles.  Is there something for quadrupole moments or does that need to be added?

Michael

Michael Winokur
Dept. of Physics
University of Wisconsin