Re: CCL:system size and pressure correlations in MD

On Thu, Feb 20, 2003, M Brunsteiner wrote:
 >
 > I am looking for information on pressure
 > correlations in liquds. If I did a molecular
 > dynamics simulation, how would the size of the
 > pressure fluctuations depend on the system size
 > (the box-size in an MD simulation)
 The simplest place I know to look for information on this is section 114
 of "Statistical Physics", by Landau and Lifshitz.  With some
 (seemingly
 reasonable) approximations, the mean square fluctuations in pressure
 are given by kT/(V*beta), where beta is the compressibility.  Hence,
 roughly, the pressure fluctuations should scale as the inverse square
 root of the volume.  Many moons ago, I ran some water simulations on various
 box sizes, that seemed to bear this out, but you should probably check things
 yourself.
 ..hope this helps...dac
 --
 ==================================================================
 David A. Case                     |  e-mail:      case # - at - # scripps.edu
 Dept. of Molecular Biology, TPC15 |  fax:          +1-858-784-8896
 The Scripps Research Institute    |  phone:        +1-858-784-9768
 10550 N. Torrey Pines Rd.         |  home page:
 La Jolla CA 92037  USA            |    http://www.scripps.edu/case
 ==================================================================