Gaussian wave packet and Coherent State based methods in Chemical Quantum Dynamics

A review of methods that propagate quantum wave functions with the help of trajectory guided Gaussian wave packets also known as Coherent States (CS) and their grids is presented. Semiclassical methods, such as Heller’s Thawed and Frozen Gaussian, which recover quantum information from a single quantum trajectory, are briefly reviewed. But mainly the article is focused on quantum techniques that use trajectory guided grids of Gaussian Coherent States and can be converged to exact quantum result. Particularly we focus on the methods of direct dynamics, which simulate atomistic systems in a manner similar to Classical Molecular Dynamics, but with the difference that quantum dynamics is described by an ensemble of interacting trajectories, which carry their quantum amplitudes instead of a single Newtonian trajectory. These methods have become an important tool in theory of nonadiabatic dynamics and ultrafast photochemistry.