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Re: [lammps-users] How to oscillate a wall while thermostatting
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Re: [lammps-users] How to oscillate a wall while thermostatting


From: saeed alborzi <alborzi.saeed6@...24...>
Date: Wed, 1 Nov 2017 17:24:01 +0330

Dear Professor Kohlmeyer

As you said , I compared the energy and velocity order of magnitude of the wall with and without oscillation. With a 2 angstrom amplitude and 2 fs period and no thermostatting, the maximum wall velocity is about 600 m/s and kinetic energy is about 23000 kcal/mol . With a 300K nvt thermostat and no oscillation, maximum velocity of 700 m/s and kinetic energy of 7000 kcal/mol is obtained. I think the values are not neglectable in camparison to each other. therefore I think I need to consider both fixes

On Wed, Nov 1, 2017 at 3:27 PM, saeed alborzi <alborzi.saeed6@...24...> wrote:
let me refer to an article titled "Static and dynamic behavior of water droplet on solid surfaces with pillar-type nanostructures from molecular dynamics simulation"

 at : http://www.sciencedirect.com/science/article/pii/S0017931014007455

this is similar to my case except that I want to add heat transfer to the simulation.

I was thinking that if it was possible to add some amount to the surface atoms' velocity as oscillating velocity while it is not rescaled by fix nvt , it would be easy to implement. but the only problem is that the "velocity set v_vx v_vy v_vz sum yes" command does not take a time-dependent value.

I apologize if I could not explain my meaning clearly and strongly appreciate your help.

On Wed, Nov 1, 2017 at 3:08 PM, Axel Kohlmeyer <akohlmey@...24...> wrote:
On Wed, Nov 1, 2017 at 7:31 AM, saeed alborzi <alborzi.saeed6@...24...> wrote:
> it was just an example, not the real case.
> the effect of frequency value will be investigated

if the frequency is (much?) lower, then - as i have already pointed
out - there is no need to do both at the same time, as the time scales
are sufficiently decoupled.

what you are asking is a technically complex and difficult process to
implement correctly.
i am not going to spend any more time and effort on this until i am
convinced that the outcome is physically meaningful.

axel.


>
>> with a 500GHz motion?? how is that possible?




--
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.