Hi, I have figured the problem. Can't use NA+/CL- in the latest version, and have to use NA/CL at least in OPLS. Best, Simon -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20100920/54822794/attachment.html>