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Re: [lammps-users] Fix rigid and minimization
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Re: [lammps-users] Fix rigid and minimization

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Wed, 02 May 2018 17:44:01 +0000

Simulated annealing is your only option. Supporting rigid body motion in the general case for minimization is non-trivial. 

Simulated annealing means you start an MD and you gradually remove kinetic energy, e. g. by applying a friction force. 

There should be plenty textbook information about this. 

Dr. Axel Kohlmeyer  akohlmey@...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

On Wed, May 2, 2018, 12:34 Mohammad Rasool Vazirisereshk <mvazirisereshk@...24...> wrote:
Hi everyone,

I am trying to perform a molecular static simulation for a group of atoms residing on a substrate (both atom types are Copper). I am forced to keep the top group of the atoms as rigid (they need to have rigid body movement). I would like to use fix rigid however this fix is not invoked during the minimization. I cannot use fix setforce 0 0 0 instead of fix rigid because these atoms are coupled with spring to another atom and therefore the force applied to the rigid group cannot be ignored. 

Is there any workaround to have fix rigid and minimize working together? I know this might be a long shot but has anyone written/modified the LAMMPS minimize to include fix rigid? Looking at the mailing archives, I saw "simulated annealing MD run" might work instead of minimization. Can someone explain to me what annealing MD is?

Thank you in advance.

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