GROMOS 54A7 angle types ga_13 and ga_15 seem to be both applicable to (straight or branched) aliphatic compounds. The force constant is the same but the equilibrium angle slightly differs from 109.5 to 111.0 degrees. I suppose that this difference accounts for the steric hindrance that makes the angles of an aliphatic C atom deviate from the ideal tetrahedral value when it is bonded to different substituents. However, the GROMOS forcefield or the related papers do not suggest in which cases each angle type should be used. Any suggestions?
I have noticed that there is also some confusion in literature. Schuler et al. [J. Comput. Chem. 22, 1205-1218 (2001)] used ga_13 for CHn-CH0-CHn and CHn-CH1-CHn while they used ga_15 for CHn-CH2-CHn. Hoeltje et al. [Biochim. Biophys. Acta 1511, 156-167 (2001), available from http://lipidbook.bioch.ox.ac.uk ], in his popular model for cholesterol, followed a different approach. Thank you for any ideas! -- View this message in context: http://gromacs.5086.n6.nabble.com/GROMOS-angle-type-ga-13-or-ga-15-tp5000819.html Sent from the GROMACS Users Forum mailing list archive at Nabble.com. -- gmx-users mailing list [email protected] http://lists.gromacs.org/mailman/listinfo/gmx-users * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/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/Support/Mailing_Lists
