[Pw_forum] Re: NVT dynamics

[Antonio Tilocca]

Dear Nichols,

> Is the c.o.m. velocity a conserved quantity in NVT dynamics?
> For example, if the c.o.m. velocity is initially zero should it stay that
> way for the rest of the simulation?

The total linear momentum is conserved in MD (see Allen-Tildesley book):
therefore, if the initial CM velocity was set to zero, the
constant (zero) linear momentum leads to no overall c.o.m.
translation along the trajectory.
So, the answer to your question should be yes, in principle.
I also seem to remember that, somewhere in cp.x, ionic positions are
readjusted in order to keep the center of mass fixed after every step,
but I don't know if this feature is still active.

Hope this helps,
Antonio

Antonio Tilocca
Department of Chemistry
University College London



> --__--__--
>
> Message: 4
> Date: Tue, 27 Feb 2007 11:13:40 -0500
> From: "Nichols A. Romero" <naromero at gmail.com>
> To: pw_forum at pwscf.org
> Subject: [Pw_forum] NVT dynamics
> Reply-To: pw_forum at pwscf.org
>