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> Date: Thu, 31 Aug 2006 17:38:37 +0200<BR>> From: lists@vrbka.net<BR>> To: gmx-users@gromacs.org<BR>> Subject: [gmx-users] own forcefield and pairs<BR>> <BR>> hi guys,<BR>> <BR>> i have (probably stupid) question, but i'm struggling with it for some <BR>> days now without success...<BR>> <BR>> i want to create a forcefield. everything is ok except the pairs, of <BR>> course. the forcefield should be used for simulations with a specific <BR>> water model (nada and van der eerden 6 center) - works fine - and some <BR>> 'contaminant' - nacl (that's easy) and probably simple aliphatic <BR>> alcohols - and here comes the problem.<BR>> <BR>> relevant excerpts from the topology are pasted at the end (some numbers <BR>> are probably wrong, so don't count on the factual correctness of the <BR>> potential).<BR>> <BR>> the alcohol 'strategy' is taken from the ffgmx file (i.e. CH3 as a <BR>> single atom). now if i use gen-pairs yes, i guess i shouldn't have the <BR>> [pairs] section for the 5OL. with gen-pairs=no, i should probably have <BR>> the [pairs] section for all 1-4 interactions. but what values should be <BR>> given for the [pairs] section c6 and c12 parameters? the example in <BR>> manual (urea) has all zeroes there, however i don't know whether it's <BR>> intentional or not.<BR>> <BR>> funny enough, all 3 possibilities (gen-pairs yes, no [pairs]; gen-pairs <BR>> no, [pairs]; gen-pairs no, no [pairs]) give me the same numbers... but <BR>> that might be as well as a consequence of the initial structure...<BR>> <BR>> so i'm confused now and i don't know what setup is the correct one. i <BR>> would be really glad if someone could point me in the right direction....<BR>> <BR>> thanks in advance. best regards,<BR>> lubos<BR>> <BR>> >>>>>>>>>>>>>>> excerpts from the topology follow<BR>> <BR>> [ defaults ]<BR>> ; nbfunc comb-rule gen-pairs fudgeLJ fudgeQQ<BR>> 1 2 yes 1.0 1.0<BR>> <BR>> ;<BR>> [ atomtypes ]<BR>> ...<BR>> ;<BR>> ; organic contaminant<BR>> ffv_ch2 CH2 14.02700 0.000 A 0.90975E-02 0.35333E-04<BR>> ffv_ch3 CH3 15.03500 0.000 A 0.88765E-02 0.26150E-04<BR>> ffv_oh OH 15.99940 0.000 A 0.22617E-02 0.15062E-05<BR>> ffv_hh HH 1.00800 0.000 A 0.00000E+00 0.00000E+00<BR>> <BR>> [ moleculetype ]<BR>> ; molname nrexcl<BR>> 5OL 3<BR>> <BR>> [ atoms ]<BR>> ; id at type res nr resname at name cg nr charge<BR>> 1 ffv_hh 1 5OL HH 1 0.398<BR>> 2 ffv_oh 1 5OL OH 1 -0.548<BR>> 3 ffv_ch2 1 5OL C01 1 0.150<BR>> 4 ffv_ch2 1 5OL C02 1 0.000<BR>> 5 ffv_ch2 1 5OL C03 1 0.000<BR>> 6 ffv_ch2 1 5OL C04 1 0.000<BR>> 7 ffv_ch3 1 5OL C05 1 0.000<BR>> <BR>> [ bonds ]<BR>> ; ai aj funct b0 kb<BR>> 1 2 1 0.10000 313800.<BR>> 2 3 1 0.14300 334720.<BR>> 3 4 1 0.15300 334720.<BR>> 4 5 1 0.15300 334720.<BR>> 5 6 1 0.15300 334720.<BR>> 6 7 1 0.15300 334720.<BR>> <BR>> [ angles ]<BR>> ; ai aj ak funct th0 cth<BR>> 1 2 3 1 109.500 397.480<BR>> 2 3 4 1 109.500 460.240<BR>> 3 4 5 1 111.000 460.240<BR>> 4 5 6 1 111.000 460.240<BR>> 5 6 7 1 111.000 460.240<BR>> [ dihedrals ]<BR>> ; ai aj ak al funct phi cp mult<BR>> 1 2 3 4 1 0.000 1.255 3<BR>> 2 3 4 5 1 0.000 5.858 3<BR>> 3 4 5 6 1 0.000 5.858 3<BR>> 4 5 6 7 1 0.000 5.858 3<BR>> <BR>> ;[ pairs ]<BR>> ; ai aj funct c6 c12<BR>> ; 1 4 1 0.0 0.0<BR>> ; 1 5 1 0.0 0.0<BR>> ; 1 6 1 0.0 0.0<BR>> ; 1 7 1 0.0 0.0<BR>> ; 2 5 1 0.0 0.0<BR>> ; 2 6 1 0.0 0.0<BR>> ; 2 7 1 0.0 0.0<BR>> ; 3 6 1 0.0 0.0<BR>> ; 3 7 1 0.0 0.0<BR>> ; 4 7 1 0.0 0.0<BR>> <BR>> -- <BR>> Lubos _@_"<BR>> http://www.lubos.vrbka.net<BR>> _______________________________________________<BR>> gmx-users mailing list gmx-users@gromacs.org<BR>> http://www.gromacs.org/mailman/listinfo/gmx-users<BR>> Please don't post (un)subscribe requests to the list. Use the <BR>> www interface or send it to gmx-users-request@gromacs.org.<BR>> Can't post? Read http://www.gromacs.org/mailing_lists/users.php<BR><br /><hr />Search from any Web page with powerful protection. Get the FREE Windows Live Toolbar Today! <a href='http://get.live.com/toolbar/overview' target='_new'>Try it now!</a></body>
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