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Re: [ESPResSo-devel] Local stress tensor/Multibody interaction and A bug

From: Christoph Junghans
Subject: Re: [ESPResSo-devel] Local stress tensor/Multibody interaction and A bug in tensor distribute
Date: Tue, 16 Jun 2009 17:03:05 +0200
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Hi Zunjing,

1) Checking with the newest released version Espresso-2.1.2j, I found that
it does not include any 3-body or higher-order interactions, eg. Angle
bending, Dihedrals. Has any Espresso developer ever coded this part? If not,
then when involving any three-body interactions, how reliable about the
results of stress tensor with current Espresso?

I guess the main point was that the angle bending doesn't contribute to the pressure. And that is why nobody has implemented the virials for these interactions till now. It will depend very much on the system you study how reliable the results are without these contributions.

Does anyone know that who coded this part and how this value "0.0000000001"
was decided? Will it be effected by compiler or machine? For my system, this
value "0.0000000001" sounds too small, leading to crash of Espresso when
computing local stress tensor.

Ben has implemented the local stress tensor in Sept 2007. And this is a feature not a bug! It seem like something went wrong in the case of your simulation. Ok "0.0000000001" is not the best choice. It should be ROUND_ERROR_PREC (see config.h) instead, which is 1e-14 by default and even smaller.



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