Inertial effects in butane stochastic dynamics

The range of validity of diffusive algorithms is studied by comparing the isomerization rates and rotational reorientation times from a series of Langevin dynamics trajectories of butane with the results of a Brownian dynamics (diffusive) trajectory, as well as with analytic approximations. It is found that inertial effects may be ignored for rotation at most liquid densities and contribute approximately 10% to the isomerization rate at water viscosities. For neat butane, or other short-chain alkane solvents at room temperature, the effect of inertial terms on isomerization rates is significant.