[gmx-users] SD velocity correction
Berk Hess
gmx3 at hotmail.com
Wed Oct 29 12:12:00 CET 2003
>I am using sd for my simulations and have a question about it. Could
>someone explain to me why the kinetic energy is corrected for the
>friction and where the form of the correction (i.e. exp(-e
>delt)+sqrt(2)(1-exp(-e delt)) comes from?
When the friction is very high, the directions of v(t-dt/2) and v(t+dt/2)
are almost not correlated. If one still wants a measure fot the velocity
at time t, the average needs to be corrected by sqrt(2).
The deterministic component of the velocity is exp(-xi dt) and
the random component is 1-exp(-xi dt).
Note that this correction only influences the kinetic energy output values
and temperature output values, and in no way influences the simulation
itself.
Berk.
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