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Re: [lammps-users] Angular velocity for calculation of rotational density of state function
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Re: [lammps-users] Angular velocity for calculation of rotational density of state function

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Fri, 25 Aug 2017 13:56:03 -0400

On Fri, Aug 25, 2017 at 12:22 PM, Arif Abdullah Rokoni <abdullah5687@...24...> wrote:
Dear LAMMPS users

I am trying to calculate entropy from MD simulation using lammps software. For that, I need to know the angular velocity and principle moment of inertia for each molecules. I am using TIP4P-Ew rigid water model, with atom style full. Is it possible to calculate angular velocity of each molecule or dump the angular velocity using lammps? I looked at the manual and found I need to change atom style from full to body. Do I need to the data file for that?

​this is nonsense. atom style full will work fine.​ atom style body is mean for *very* different purposes.
I also tried to use thus:
"compute cc1 all chunk/atom molecule"
But looks like style "molecules" is not appropriate for my case.

​you have not read the documentation with sufficient care. this is *exactly* what you need. this will define chunks, where each chunk is a molecule. for those chunks you can then do computations like inertia/chunk or angmom/chunk, which will compute the desired properties for each chunk.​ chunks allow to flexibly and dynamically group atoms and then do computations on them. this is a very general and flexible concept that avoids having to re-write analysis computes depending on how things are grouped.

so please review the manual again and pay special attention to the "chunk" feature and you'll see.



It will be great if someone can assist me on that. Thank you very much.

Best Regards
Arif Abdullah Rokoni

Complex Fluids and Multiphase Transport Lab, Science Center
Mechanical Engineering and Mechanics Department
Drexel University

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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.