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

From: Jerome Henin (
Date: Thu Oct 23 2008 - 10:11:33 CDT

Hi Fred,

If you satisfy these conditions:
1) namd set to NVE, i.e. don't enable any thermostat or barostat
2) the external forces derive from a potential
3) the time step is small enough

then you should have energy conservation. You can have NAMD take your
external potential into account in its output using the addenergy


On Wed, Oct 22, 2008 at 11:48 PM, Fred (Rui FENG) <> wrote:
> Hi all,
> I'm trying to add an external force on all atoms to move them. The
> force field among them is just Lennord Jones. They are accelerated,
> but I need to keep their velocity constant. I cannot just use
> "RescaleTemp" to keep the kinetic energy constant. Because if I do
> that, the total energy will increase. I think what I really need to do
> is to keep total energy (both VDW energy and kinetic energy) constant.
> That equals drawing out the work that the external force made. Could
> you tell me what parameters are in charge of that function? Thank you
> so much!
> Have a nice day!
> Fred

This archive was generated by hypermail 2.1.6 : Wed Feb 29 2012 - 05:21:25 CST