pair_style and integration nvt or nve

Submitted by rasoul on Wed, 08/21/2013 - 14:55

I have a question about pair_style. I'd like to simulate solid materials such as shale, clay, sand, and like this. I need to know what the appropriate pair_style for doing that is?

Another question is about integration. In my project I have to decrease temperature from X1 to X2. How can I do that?
And using "fix integer nvt/sphere temp X1 X2 DX" is true or not?

Thanks a lot for the response in advance.

moritzhoefert | Tue, 08/27/2013 - 13:05

Hi rasoul,

NVT ensembles are usually used for molecular dynamics and I think it does not make sense to use that for DEM simulations. In MD temperature is a directly accessible quantity: the velocity fluctuations of atoms. And the thermostat is applied to those. In DEM temperature is a per particle quantity independent of the velocities.

You could use fix nve/sphere to propagate the trajectories of DEM particles and heat/gran/conduction to track temperature.


rasoul | Tue, 08/27/2013 - 22:47

Thanks a lot for the response. So, how can I fix temperature in a target point or decrease it slowly?

ckloss's picture

ckloss | Fri, 08/30/2013 - 15:15

Hi rasoul,

as Moritz said, NVT is for molecular dynamics, and temperature here is temperature in the sense of kinetic gas theory, which is not approropriate in this case

have a look at the heat transfer tutorials that come with LIGGGHTS.
with the "set" command, you can set the temperature of particles as you desire