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NVE ensemble

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The microcanonical or NVE ensemble can be obtained in the following ways:

  • Set SMASS=-3 and specifying MDALGO=2 (or 0).
  • Set ANDERSEN_PROB=0.0 while using the Andersen thermostat (MDALGO=1). This is a special case for the thermostat where the probability of collision with the heat bath is set to zero, which enables a fully correct sampling of the microcanonical ensemble.

The following table shows the possible ensemble and thermostat combinations in VASP:

Thermostat
Ensemble Andersen Nose-Hoover Langevin Multiple Andersen
NVE MDALGO=1, ANDERSEN_PROB=0.0
NVT MDALGO=1 MDALGO=2 MDALGO=3 MDALGO=13
ISIF=2 ISIF=2 ISIF=2 ISIF=2
NpT not available not available MDALGO=3 not available
ISIF=3
NpH MDALGO=3, ISIF=3, LANGEVIN_GAMMA_L=0.0