Spikes in the Energy Plot

From: Viswanath Pasumarthi (v.pasumarthi_at_iitg.ernet.in)
Date: Mon Feb 09 2015 - 02:26:08 CST


I've been trying to equilibrate the pure ionic liquid (TDTHP-DCA) system
to estimate molar volume, self-diffusion constant etc. But, there are
spikes arising in the energy plot. After initially observing these spikes
when running the simulation with 1 fs timestep, I repeated the simulation
by optimizing the initial structure again, and changed the timestep to 0.5
fs. This time I save veldcd file to see if there are any abnormalities in
velocities at the instants spikes are arising. Now, even at 0.5 fs
timestep, spikes continue to exist, moreover, now the energy of the system
is positive. I compared the velocities between the normal instants and
instants where spikes are observed in terms of maximum value, mean and
standard deviation. And these values are quite relatable, proving there
are no abnormal velocities at the spiked instants. What could be the
reason for this behavior and how to solve?

PE_1 fs:

PE_0.5 fs:


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