[Pw_forum] Energy conservation in Verlet-MD?

[Norbert Nemec]

Hi there,

I am trying a very simple MD calculation (optical phonon mode of Silicon, similar to the original Car-Parinello paper). I am surprised that the total energy is not constant but oscillates with about 10% of the amplitude of the potential energy.

This oscillation is *independent* of the MD time step. Furthermore it did not change with the k-grid, the energy cutoff, the functional or the pseudopotentials.

Attached is one of the input files that I used.

Does anyone know what might cause this behavior?

Greetings,
Norbert
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