  Semiclassical approximations for quantum dynamic simulations in complex
chemical systems range from rigorously accurate methods that are
computationally expensive to methods that exhibit near-classical scaling with
system size but are limited in their ability to describe quantum effects. In
practical studies of high-dimensional reactions, neither extreme is the best
choice: frequently a high-level quantum mechanical description is only required
for a handful of modes, while the majority of environment modes that do not
play a key role in the reactive event of interest are well served with a lower
level of theory. In this feature we introduce Modified Filinov filtration as a
powerful tool for mixed quantum-classical simulations in a uniform
semiclassical framework.
