From chemistry-request@server.ccl.net Thu Jul 27 11:30:58 2000 Received: from mailhost.msi.com (fire.msi.com [146.202.0.242]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id LAA23520 for ; Thu, 27 Jul 2000 11:30:57 -0400 Received: (from daemon@localhost) by mailhost.msi.com (980427.SGI.8.8.8/970903.SGI.AUTOCF) id IAA28987 for ; Thu, 27 Jul 2000 08:26:57 -0700 (PDT) Received: from unknown(146.202.11.79) by mailhost.msi.com via smap (V2.0) id xma028983; Thu, 27 Jul 00 08:26:44 -0700 Message-Id: <4.3.1.2.20000727082144.00b7e100@146.202.6.130> X-Sender: dgregory@146.202.6.130 X-Mailer: QUALCOMM Windows Eudora Version 4.3.1 Date: Thu, 27 Jul 2000 08:26:11 -0700 To: CHEMISTRY@ccl.net From: Don Gregory Subject: Re: CCL:Dielectric in Charmm In-Reply-To: <398012BA.B81973E4@ucl.ac.uk> References: <397F537A.6C76C8CD@chem.ufl.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Hi Michael, and Xiang, I would only slightly disagree with Michael's statement that "it is questionable to set these parameters to a value other than one" in that what one should generally use, are those parameters that were used to optimize the force-field originally. If certain partial chargers, and/or vdw terms were adjusted with an E14FAC set to 0.5, and then you use it at 1.0, one runs the risk of over evaluating those terms. In CHARMm, one can see the 'recommended' parameter values by looking at the 'NBONDED' command section in the text version of the parameter file. Hope this helps! Don Gregory At 11:45 AM 7/27/00 +0100, Michael Brunsteiner wrote: >"Xiang(Simon) Wang" wrote: > > > > Dear CCLers, > > > > When setting up the dielectric constant in charmm, what's the difference > > between [ EPS real ] and [ E14Factor real ]? > >i believe that E14Factor only applies to 1-4 interactions, >i.e. interactions between atoms in the same molecule separated by >three bonds ... however, it is questionable to set these parameters >to a value other than one anyway ... >i'd always let EPS = E14Factor = 1.0 and use Ewald summation. > >mic > > > >=========================================================== >Writing software is more fun than working. > >---------------------------------------- >Michael Brunsteiner >Centre for Theoretical and Computational Chemistry >University College London >20 Gordon Street, London WC1H 0AJ, U.K. >mailto:m.brunsteiner@ucl.ac.uk >http://www.unet.univie.ac.at/~a8805193 >---------------------------------------- > >-= This is automatically added to each message by mailing script =- >CHEMISTRY@ccl.net -- To Everybody | CHEMISTRY-REQUEST@ccl.net -- To >Admins >MAILSERV@ccl.net -- HELP CHEMISTRY or HELP SEARCH >CHEMISTRY-SEARCH@ccl.net -- archive search | Gopher: gopher.ccl.net 70 >Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl@ccl.net > > > Dr. Don Gregory (dgregory@msi.com) CHARMm Product Marketing Manager Molecular Simulations Inc. 9685 Scranton Rd. San Diego, CA 92121 (858) 799-5331 http://www.msi.com Mobile Ph.: (619) 200-3613