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Re: [ESPResSo] rigid_bond

From: Mikheil Azatov
Subject: Re: [ESPResSo] rigid_bond
Date: Wed, 9 Jun 2010 13:06:07 -0400

Hi Tristan,

Thank you for quick response. Rigid_bond interaction started to work but it works kinda strangely. For small system it works, but as the number of particles increases i start to get an error.
VEL CORRECTIONS IN RATTLE failed to converge after 1000 iterations !!
I found an old email from Mehmet Sayar about similar problem but I don't know if this was resolved.

Thanks, Mike

On Wed, Jun 9, 2010 at 8:46 AM, Tristan Bereau <address@hidden> wrote:
Hi Mike,

Yes, rigid bonds require a feature, called BOND_CONSTRAINT. Make sure you uncomment this before recompiling the code. I'm not very familiar with rigid bonds, but as far as I know they use an algorithm that converges the particle positions in order to satisfy the rigid bond constraint (i.e. how far should the two atoms be). This requires a positional tolerance that will stop the algorithm once the distance between the two atoms is within that tolerance. Rigid bonds also give rise to velocity constraints (the velocity of p1 and the velocity of p2 aren't independent), and require a velocity tolerance.


On Jun 8, 2010, at 11:02 , Mikheil Azatov wrote:

Hi again,

Sorry I've been asking a lot of questions lately, just started using espresso and a lot of questions appear. I tried looking through the mailist archive but I don't think this one was asked.

In the manual there is a rigid_bond bonded interaction but it's without a description. I tried using it but i receive "unknown bonded interaction type "rigid_bond" ". So I was wondering if anyone has used rigid_bond before then what features I might need to enable to make it work? Also what exactly are   positional tolerance and velocity tolerance in the definition of rigid_bond.

Thanks again for you help!

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