So, using twin-range cut-off does not violate the energy conservation for RC method, but it violates for PME method. Is this the case ?
-----Original Message----- From: David van der Spoel <[EMAIL PROTECTED]> To: Discussion list for GROMACS users <[email protected]> Date: Sat, 01 Sep 2007 14:48:03 +0200 Subject: Re: [gmx-users] r_list and r_coulomb values while using PME OZGE ENGIN wrote: > 'The force is not the derivative of the potential', is it due to the types of > calculations performed in PME, using of FFT for reciprocal sum? Because it > does not matter while using reaction-field method. > Sorry, this phenomenon is a little complicated to me :) this is only when you combine twin range (rcoulomb > rlist) and PME. then the forces for a certain distance range are not computed at each time step while the others are. you may want to (re)read the PME papers and/or the gromacs manual about twin range. > > Thanks for your attention! > > Oz. > > -----Original Message----- > From: David van der Spoel <[EMAIL PROTECTED]> > To: Discussion list for GROMACS users <[email protected]> > Date: Sat, 01 Sep 2007 13:37:05 +0200 > Subject: Re: [gmx-users] r_list and r_coulomb values while using PME > > OZGE ENGIN wrote: >> Hi all, >> >> I can not understand why it is required to take same values for both r_list >> and r_coulomb parameters when using PME for calculation of electrostatic >> interactions? >> >> I read archieve, and gromacs manual. In archieve, similar question had been >> posted, but not replied yet. >> >> Thanks in advance > > if rlist < rcoulomb you will have a twin range interaction, meaning the > atom pair interactions for distance between these two will be computed > every nstlist steps only, while the interaction beyond rcoulomb will be > computed at each time step. this will lead to bad energy conservation, > since the force is not the derivative of the potential. >> Oz. >> >> _______________________________________________ >> gmx-users mailing list [email protected] >> 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 > > -- David van der Spoel, Ph.D. Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University. Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. Fax: +4618511755. [EMAIL PROTECTED] [EMAIL PROTECTED] http://folding.bmc.uu.se _______________________________________________ gmx-users mailing list [email protected] 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 _______________________________________________ gmx-users mailing list [email protected] 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
