A potential used to give an approximate description of the potential energy interaction, V, of molecules as a function of intermolecular distance r. The general form of the Lennard-Jones potential is V=Cn/rn – C6/r6, where Cn and C6 are coefficients that depend on the specific molecules and n is greater than 6 so that at small separations the repulsion term dominates the interaction, the r−6 term being attractive. The value n=12 is frequently chosen. In this case the Lennard-Jones potential is given by:V=4W[(r0/r)12 – (r0/r)6], where W is the depth of the potential well and r0 is the separation at which V=0. The minimum value of the well occurs at the separation re=21/6r0. The representation of the repulsive part of the interaction by a 1/r12 term is not realistic; a much more realistic term is the exponential term, exp(–r/r0), as it is closer to the exponential decay of the wave functions and thus of their overlap, which describes the repulsion.
V=Cn/rn – C6/r6
V=4W[(r0/r)12 – (r0/r)6]