fix pressure with ReaxFF

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1

Dear all,

I am trying to simulate methane molecules by using ReaxFF parameters which I had from professor van Duin. I want to run simulation at a temperature of 298K and a pressure of 1 atm. Firstly, I ran simulation with fix npt and then re-ran with nve. However, molecules just rotate without moving. Moreover, some molecules stepped out the simulation box.

I tried to run another simulation in which I used just nve and fix temp/berendsen. With this simulation, I saw molecules move randomly inside the box. I don’t know why pressure effect to the movement of molecules. Are there anything wrong with initial configuration or commands in my input file? All files are attached.

Thanks for your help
Best regards

Tran

data.CH4 (24.5 KB)

in.CH4 (1009 Bytes)

2

Tran,

3

Thank you for your reply,

I mean molecules cannot move from place to place. They just rotate around their places. And, I am using VMD to visualize.

4

Thank you for your reply,

I mean molecules cannot move from place to place. They just rotate around
their places. And, I am using VMD to visualize.

​you must be mixing something up there. i ran your input with both variants
on my machine and the only qualitative difference is that with fix npt the
system is expanding. everything else looks normal, and molecules move as i
would expect them to do under the given boundary conditions.

axel.

5

Thank you for taking the time to solve my problem.

I am trying to fix it. Actually, I have an assignment of comparing ReaxFF with other force fields by simulation of methane molecules. I got results completely different from theory and experimental data.

Kind regards,

Tran