Re: How to keep Total Energy constant when an external force is added?

From: Axel Kohlmeyer (
Date: Thu Oct 23 2008 - 09:58:15 CDT

On Wed, 22 Oct 2008, Fred (Rui FENG) wrote:

FR> Hi all,
FR> I'm trying to add an external force on all atoms to move them. The
FR> force field among them is just Lennord Jones. They are accelerated,
FR> but I need to keep their velocity constant. I cannot just use


please go back and think about this statement.
it does not make sense at all.
if you accelerate all atoms (all atoms), their
velocity _cannot_ remain constant.

perhaps you should first explain _what_ you want to achieve
instead of _how_, and perhaps somebody can then give some
advice of what you should do.


FR> "RescaleTemp" to keep the kinetic energy constant. Because if I do
FR> that, the total energy will increase. I think what I really need to do
FR> is to keep total energy (both VDW energy and kinetic energy) constant.
FR> That equals drawing out the work that the external force made. Could
FR> you tell me what parameters are in charge of that function? Thank you
FR> so much!
FR> Have a nice day!
FR> Fred

Axel Kohlmeyer
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
If you make something idiot-proof, the universe creates a better idiot.

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