[gmx-users] The Lennard-Jones parameter of Na+?

[Mark Abraham]

Hu Zhongqiao wrote:
> Dear all,
>  
> I find the Lennard-Jones parameter epsilon of Na+ in Gmx is very 
> different from some references.
>  
> In gmx, I calculated sigma(Na+)=0.258nm, epsilon(Na+)=0.0617 kJ/mol
>  
> But many researchers cited a paper by Dang LX [J. Am. Chem. Soc., 1995, 
> 117, 6954-6960] and used parameters as follows sigma(Na+)=0.258nm, 
> epsilon(Na+)=0.42 kJ/mol.
>  
> I want to ask where parameter of Na+ in gromos force field comes from? 
> Is it reasonable?

In isolation, no force field parameter has any meaning. See 
http://wiki.gromacs.org/index.php/Force_Fields#Usage

Mark