can you give a better description? what is the reduction in speed? you mean calculation speed, I suppose... what is your system? what is your ensemble (fix)? how is the change in neighbour lists when simulation progresses?
I am simulating some alkane molecules, with a total number of atoms to be 2000.
By reduction in speed means the steps per second. if density is high it is giving me only 1 step per sec. I am simulating in NVT ensemble. Pairwise force and energy calculation is taking the maximum time.
the higher the density, the more interatomic contacts you'll have on average, and more energy terms have to be calculated. This difference can be pretty dramatic when going from a sparse gase phase to a liquid or something.
I am aware of these things, but the decrease in speed is too much. I just wanted to know if i am making some logical mistake somewhere or is there any way to accelrate reaxff simulation in LAMMPS.