where k B represents the Boltzmann's constant, T is temperature, h is Planck's constant, R is the ideal gas constant, and ∆G ‡ is the difference in Gibbs free energy between transition state and reactant. Transition state theory requires the properties of the reactants and transition states of a reaction to be known or calculated using quantum chemistry, specifically by solving the Schrödinger equation for each of these chemical species: