Quantum Dynamic (QD) is used to study chemical reactions in the gas phase.Current computational and theoretical methods are used to calculate the rate of reactions and to predict the detail of the reactions.

Methods: For reactions with high energy barrier such as those involving bond breaking or formation, QD methods need to be used.

QD procedure: Solve Schrodinger equation to get the electronic structure. Compute  Potential Energy Surface  (PES) using ab initio electronic structure methods.  This yield reliable reaction barriers. Use these PES in the solutions of Schrodinger equation for the nuclei to predict fundamental informations of chemical reactions.

For three atoms reactions, a computer code called ABC, which involves hyperspherical coordinates, is used. This theory can be extended to full dimensions by including functions that describe molecular rotations. Agreement between this theory and experiment is remarkable. For reactions with several maxima and minima in PES, "direct dynamic" methods are sometimes used. In these methods, electronic energies are calculated directly from an ab initio code whenever they are required. However direct dynamic are difficult to aplly in QD calculations due to large number of quantum wave functions. An alternative method is used which involves solving the time dependent Schrodinger equation. This is called the "wave packet" calculations.

For four or more atoms reactions, a method is developed that allows the construction of effective Potential Surface (PS) in reduced dimensionality through a small number of accurate electronic structure calculations. These PS are used in time independent quantum scattering calculations with hyperspherical coordinates, treating only bonds broken and formed in reactions explicitly. This method is used in reaction between H atom and propane which has result agree swell with experiment. Another approach is multiconfigurational time dependent Hartree (MCTDH) which treat quantum wave functions as a product of single particles and time dependent functions. MCTDH can be used with a method for calculating the quantum fluxes in a chemical reaction to calculate the reactive rate constant of multidimensional system.