[gmx-users] Why charge parameter of cations like Cu2+, Zn2+ in GROMOS 54a7 force field in GROMACS equals to zero?

[Chenlin Lu]

Hi all,
I am trying to modify the original GROMOS 54a7 force field files implemented in GROMACS to add parameters of some new cations. But when I checked the ffnonbonded.itp, I found that the charge parameter of CU2+, Zn2+ equals to zero. Why? What does it mean? How GROMOS 54a7 force field calculate the electrostatic interaction? If I want to add some new ions, what should I do?
Thans in advance,
Chenlin

--------------------------------------------------

Chenlin Lu

Department of Chemical Engineering, 

Tsinghua University, Beijing, 100084

Tel: 86-13120180517

Email: lucl17 at mails.tsinghua.edu.cn