# How to oscillate a wall while thermostatting

you have mentioned a key point and I will consider that.

anyway is there a solution to implement both of oscillation and thermostatting together?

You have not answered my question about what you are trying to model.
Axel

I am trying to model heat transfer between a surface and a droplet on it

I am trying to model heat transfer between a surface and a droplet on it

that doesn't explain the need the move the surface.

moving helps the droplet to jump from the surface and also changes the wetting state of the droplet

moving helps the droplet to jump from the surface and also changes the
wetting state of the droplet

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

axel.

it was just an example, not the real case.
the effect of frequency value will be investigated

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.

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”

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.

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

those numbers are useless and irrelevant for the properties you want
to determine.
you have to determine the amount of energy *transferred* and in the
case of the moving wall, that requires properly dealing with the
center-of-mass bias.
it looks as if you first need to have a deep peek into a text book on
statistical thermodynamics and gain a better understanding what you
are doing.

axel.

Dear Mr.Kohlmeyer

Hello again

Does the compute group/group command calculate the “energy transferred” you said exactly?

Thanks

Dear Mr.Kohlmeyer

Hello again

Does the compute group/group command calculate the "energy transferred"
you said exactly?

​no.​

I have simulated the two case you said

1. First I relaxed a medium at T1 temperature and then put it adjacent to a solid wall and applied fix nvt at T2>T1 to the wall and fix nve to the medium.
2)Second I put the medium adjacent to an oscillating wall with 2angstrom and 2ps.

I observed that the medium is leaving the surface more quickly in the 2nd case than the 1st case and its kinetic energy is rapidly rising.

So ,as you said , the oscillation is the dominant energy transferring source with that amplitude and period.

am I right?