RPMD Integrator Doesn't Conserve Center of Mass Motion
Posted: Fri Jun 16, 2023 11:47 am
Hi Peter,
I have been using the RPMD Integrator and I found that if you run the simulation for more than a couple of ns, the center of mass motion of the system drifts. This happens if you are using the CUDA platform and the precision is set to single or mixed. Interestingly, if you specify only 1 copy (P = 1), the system doesn't drift. This only happens if you use a P > 1. [P is the number of replicas]. I should also remark that if you use double precision, there is no drift [MSD ~ 1e-5].
At the moment, I'm not sure how to handle this issue. I've checked and the CMMotionRemover force is being added to the system. I wrote my own script to remove the drift from the system [i.e., every 100 steps, I calculate the center of mass velocity and rescale the particle velocities] and this didn't make a difference.
Any ideas on how I can fix this issue?
Ali
I have been using the RPMD Integrator and I found that if you run the simulation for more than a couple of ns, the center of mass motion of the system drifts. This happens if you are using the CUDA platform and the precision is set to single or mixed. Interestingly, if you specify only 1 copy (P = 1), the system doesn't drift. This only happens if you use a P > 1. [P is the number of replicas]. I should also remark that if you use double precision, there is no drift [MSD ~ 1e-5].
At the moment, I'm not sure how to handle this issue. I've checked and the CMMotionRemover force is being added to the system. I wrote my own script to remove the drift from the system [i.e., every 100 steps, I calculate the center of mass velocity and rescale the particle velocities] and this didn't make a difference.
Any ideas on how I can fix this issue?
Ali