Hi Dr.Abraham Thank you very much for your answer
yas I 've extacted configuration with 0.2 nm distance and when I want to run NPT for first configuration,I gave that error. I didn't undersatnd this mdp file for this step, I got this file from umbrella sampling tutorial and I adjusted for my system but I didn't understand we are doing a pullind simulation with zero velocity, I think the aim is to costriant structure by artifial spring but we don't move it, am I right? Thank you very mmuch for your anwer, your help and your time Regards Azadeh -- This email was Anti Virus checked by Security Gateway. -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.