The parameters of the GROMOS96 force field governing dihedral angle transit
ions in aliphatic chains have been reconsidered, since these parameters pro
duce a too large ratio of trans to gauche conformations in such chains. A r
efined set of parameters for dihedral angle interactions and third-neighbou
r interactions involving CH2 and CH3 atoms is proposed. They were obtained
by fitting to the heat of vaporization, pressure and trans-gauche ratio for
liquids of three n-alkanes, n-butane, n-pentane and n-hexane. The new para
meter set does reproduce better these quantities and should therefore be mo
re appropriate for use in simulations of polymers and membranes. A comparis
on of the mentioned properties obtained from simulations with united-atom m
odels and from simulations with an all-atom model shows that the latter doe
s not necessarily yield an improved description of molecular behaviour.