Subject: Re: CCL:LJ forcefield for K+

From: Bill Ross <[email-masked]>
Date: Thu, 20 Dec 2001 14:42:05 -0800 (PST)

does anybody has a LJ potential for the K+ cation,
	I want to simulate an aqueous solution containing
	the K+ ion.  I know of a reference Physica B & C
	1985, 131, 196, but it is out of reach.  
	
It depends on the water model, and also on the combining
rules used for mixing the LJ with the water LJ. See

  Ross, W.S. and Hardin, C.C., J.  Am.  Chem.  Soc.   116, 6070-6080  (1994).  

We discovered that various parameters seem to work equally well.
The commonly-used parameters for K+ are those of Aqvist, but simpler
ones give indistinguishable results for free energy and radial
distribution. We also had to convert the Aqvist parameters for use
with the combining rules used in the Amber programs. And different
parameters were necessary for ion interactions with non-TIP3 atoms.

Bill Ross