Dear Mark Thanks for your reply.
In more detail, I used ffg43a1 force field. In the file ffG43a1nb.itp, one can find the Lennard-Jones parameters for Na+ as follows: C6=7.2063121e-05; and C12= 2.1025e-08 >From these 2 values one can get epsion(Na+)=0.0617 kJ/mol. Because the force field parameters for ions is relatively simple, the main interaction of Na+ with other particles is electrostatic and van der Waal's forces. And I also believe that the combination rule makes not big difference for different force fields in this case. It is strange epsion(Na+) = 0.0617 kJ/mol in ffg43a1 is very different from some references (for example, in the paper shown in my last email, this value is epsilon(Na+) = 0.42 kJ/mol ). So I just want to know how the developers of gmx or gromos force field get Lennard-Jones parameters for Na+. Zhongqiao > 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 _______________________________________________ gmx-users mailing list gmx-users@gromacs.org http://www.gromacs.org/mailman/listinfo/gmx-users Please search the archive at http://www.gromacs.org/search before posting! Please don't post (un)subscribe requests to the list. Use the www interface or send it to [EMAIL PROTECTED] Can't post? Read http://www.gromacs.org/mailing_lists/users.php
