Semiclassical tunneling calculations

We show that a semiclassical approximation for calculating thermally averaged transition-state-theory transmission coefficients for realistic effective potential energy barriers for a separable reaction coordinate generally provides accuracy of 10% or better compared to accurate quantum mechanics for the same potential energy barrier. This error is smaller than the error generally caused by the separable approximation itself. We show how to perform the semiclassical calculations conveniently and efficiently.