The molecular dynamics simulation of a methyl group in water was repeated using slightly different parameters to ensure that there are no major errors in the results. It has also been proven explicitly that a generalized Langevin equation or any other Gaussian random process cannot reproduce the simulation results. A quantum mechanical model extrapolated to the classical limit, however, reproduces the simulation results quite well. But the quantum mechanical model cannot be extended to larger molecules because the dimensions of the matrices involved quickly become too large. Consequently, we are developing a variation on Skinner and Wolynes collision kernel that includes a memory function. This formulation appears to have a structure that is closer to the quantum mechanical model than any simple variations on the generalized Langevin equation. Development of this model continues.
