Which thermodynamic ensemble does Gaussian's BOMD functionality sample?

Question

Someone sent me a Born-Oppenheimer molecular dynamics output with the following settings line:

# b3lyp/sto-3g BOMD=(MaxPoints=35, Ntraj=1, Update=15, RTemp=298) guess=read geom=allcheck

Based on my understanding of the BOMD keyword documentation, it sounds like the temperature is only used for putting energy into the vibrational modes, which are then used to initialize the nuclear velocities. Since there is no mention of a thermostat in the output or the documentation, this implies that calculations can only be run in the NVE ensemble.

Are my assumptions correct?

Answer 1

@pentavalentcarbon: As of now (Gaussian16), I believe that BOMD calculations can only be run in the NVE ensemble.

However, you can do ADMP (also available with Gaussian and uses an extended Lagrangian scheme), and offers equivalent functionality to BOMD. Thermostatting is available here, but the caveat is it implements only the simple velocity rescaling algorithm. On performing simple tests this seems to be "nearly" canonical on some systems I have worked on. i.e small ion-water clusters.