Subject: CCL: Spherical truncation in simulations

From: [email-masked] (Ricardo)
Date: Sat, 20 Apr 96 11:19 BST

Dear netters,

        I'm simulating water using the Ewald sum, on one hand, and using a
straight spherical truncation of the electrostatic interactions, on the
other.  I'm doing NPT Monte Carlo runs near room temperature. 
        My problem is that, while I get the right density using the Ewald
sum, when I use spherical truncation the density is smaller by about 10%.
Is this sort of effect to be expected when long-range forces are treated by
simply truncating them at a given cutoff?
	Any comments and/or references would be much appreciated.

	R. L. Mancera
	Department of Chemistry
	University of Cambridge
	Lensfield Road
	Cambridge CB2 1EW, UK

	Tel:  +44 1223 336353
	Fax:  +44 1223 336362
	E-mail:  [email-masked]