Reaxff c/h/o energy conservation and temperature drift in NVE

The ReaxFF combustion force field was fitted to describe the combustion of hydrocarbons, not graphene oxides. You might just be using a force field that is not appropriate for your simulation.

Ray

The Chenoweth CHO parameters have some pretty steep gradients, and usually requires smaller than typical time steps for energy conservation. I wouldn’t be surprised if 0.5 fs was still to large. I’d rerun with decreasing time steps and look for convergence.
-Ben

Hi all,

Thanks for the replies! Sorry, 1 small correction, the timestep I used was 0.25fs. The times should be divided by half.

I have tried adjusting the timestep to half (0.125fs) during the NEMD step for a smaller system. The two attached files are both equilibrated at 0.25fs timestep, but one is ran with NEMD using 0.125fs, and one is using 0.25fs. Interestingly, I get even more drift. It could be also dependent on the specific velocity configuration. I have seen the similar behaviour with a separate series of repeated runs, only changing the inital velocity seed. Some systems had drift, while others had less.

Thomas

02_length_05nm_01fs.mp_temp-plots.png

02_length_05nm_hc_out.mp_temp-plots.png