Subject: Re: MD or MC

From: [email-masked] (Slawomir Blonski)
Date: Wed, 9 Nov 1994 15:20:13 -0500 (EST)

Q:
> 	   Which one, MD or MC, you will select if CPU time-constraint
>    is imposed ? 
A:
> The choice between MD and MC depends not on your CPU time allocation,
> but on the problem you want to solve. 

There is a class of Monte Carlo simulations which can be directly compared
with molecular dynamics. These are the MC studies of time-dependent phenomena.
See for example works on polymer reptation by Kurt Binder or on biopolymers
by team Skolnick - Kolinski. In such an approach, a new MC configuration is 
formed from the previous one (after being accepted with Metropolis criterion). 
This may be assumed to be equivalent to a time evolution of the system. Because
changes in the system between consecutive MC configurations are greater than
after a single MD time step, one can treat the MC step as a time period much
longer than the MD time step. In this way, the time-dependent MC simulations 
extend longer in time than the MD with the same number of steps, although 
the exact length of the MC time step is hard to estimate and MC gives only
positions of the particles, but not the momenta. However, MC may be preferred 
over MD, if one simulates large systems with long relaxation times which are
beyond reach of current computers.

Slawomir Blonski

PS. I use molecular dynamics.