Condensed phase quantum-classical framework

We present an overview of variational transition state theory from the perspective of the dynamical formulation of the theory. This formulation provides a firm classical mechanical foundation for a quantitative theory of reaction rate constants, and it provides a sturdy framework for the consistent inclusion of corrections for quantum mechanical effects and the effects of condensed phases. A central construct of the theory is the dividing surface separating reaction and product regions of phase space. We focus on the robust nature of the method offered by the flexibility of the dividing surface, which allows the accurate treatment of a variety of systems from activated and barrierless reactions in the gas phase, reactions in rigid environments, and reactions in liquids and enzymes. 

Reaction processes in condensed phase are a major challenge. To describe reactions in solution, one either has to resort to classical mechanics or has to include the coupling to the enviroment in a quantum simulation. Flux correlation functions provide a suitable theoretical framework for this purpose. However, the description of system-bath couplings in realistic quantum systems still is a serious theoretical problem and only first steps in this direction have been taken. 

---