The discussion focuses on the calculation of the center of mass (COM) velocity in molecular dynamics (MD) simulations. It highlights the common practice of subtracting the average velocity from each atom's velocity to ensure the COM velocity is zero. The participants clarify that the mass-weighted average velocity is equivalent to the COM velocity, emphasizing the importance of using total mass rather than the number of atoms for accurate calculations. This understanding is crucial for accurate MD simulations.
PREREQUISITESThis discussion is beneficial for molecular dynamics researchers, computational chemists, and anyone involved in simulating physical systems who seeks to understand the implications of center of mass velocity adjustments in their simulations.
Can you see that the [mass-weighted] average velocity is equal to the velocity of the center of mass?xperrylinn said:When calculating the center of mass for an MD simulation, I've seen a few codes that subtract the average velocity from each atoms velocity. I think the reasoning behind this is that you want the velocity of center of mass for the simulation to be zero, which I understand, but I don't understand computationally how subtracting the average velocity from each velocity achieves this.
The correct way to compute a weighted average is to divide by the sum of the weights, not the count of items.xperrylinn said:mass-weighted average velocity = (sum each atom's momentum) / (num atoms)