>Dear users: >I want to know how to fix the com of the group in the pull or afm simulation,Please give some ideas. comm-grps in grompp.mdp, isn't it? -- Vitaly V. Chaban School of Chemistry National University of Kharkiv Svoboda sq., 4, Kharkiv 61077, Ukraine email: chaban at univer.kharkov.ua skype: vvchaban