Chapter 10: Quantum-dynamical Calculation of Rate Constants in Polyatomic Reactions Employing the Quantum Transition State Concept

This chapter describes efficient ways to obtain thermal and microcanonical rate constants from rigorous quantum dynamics simulations. The quantum transition state concept is introduced, which is based on flux–flux correlation functions and a wavepacket representation of the thermal flux operator. Different aspects of the utility of the quantum transition state concept are discussed. Numerically efficient ways to calculate the required eigenstates and wavepacket propagations are discussed. In particular, the multiconfigurational time-dependent Hartree approach, which allows for the full-dimensional treatment of polyatomic systems, is discussed in detail, and several extensions of the approach are introduced. The efficency of the techniques introduced in the chapter is exemplified by discussing prototypical tri-, tetra- and six-atomic reactions.