quantum Monte Carlo methods, are also possible and are particularly useful for describing equilibrium distributions of states. Adiabatic chemical dynamics In adiabatic dynamics, interatomic interactions are represented by single scalar potentials called potential energy surfaces. This is the Born–Oppenheimer approximation introduced by Born and Oppenheimer in 1927. Pioneering applications of this in chemistry were performed by Rice and Ramsperger in 1927 and Kassel in 1928, and generalized into the RRKM theory in 1952 by Marcus who took the transition state theory developed by Eyring in 1935 into account. These methods enable simple estimates of unimolecular reaction rates from a few characteristics of the potential surface. Non-adiabatic chemical dynamics Non-adiabatic dynamics consists of taking the interaction between several coupled potential energy surface (corresponding to different electronic quantum states of the molecule). The coupling terms are called vibronic couplings. The pioneering work in this field was done by Stueckelberg, Landau, and Zener in the 1930s, in their work on what is now known as the Landau–Zener transition. Their formula allows the transition probability between two diabatic potential curves in the neighborhood of an avoided crossing to be calculated. Spin-forbidden reactions are one type of non-adiabatic reactions where at least one change in spin state occurs when progressing from reactant to product. See also Atomic physics Computational chemistry Condensed matter physics Car–Parrinello molecular dynamics Electron localization function International Academy of Quantum Molecular Science Molecular modelling Physical chemistry List of quantum chemistry and solid-state physics software QMC@Home Quantum Aspects of Life Quantum electrochemistry Relativistic quantum chemistry Theoretical physics Spin forbidden reactions References Gavroglu, Kostas; Ana Simões: Neither Physics nor Chemistry: A History of Quantum Chemistry, MIT Press, 2011, Karplus M., Porter R.N. (1971). Atoms and Molecules. An introduction for students of physical chemistry, Benjamin–Cummings Publishing Company, Considers the extent to which chemistry and especially the periodic system has been reduced to quantum mechanics. External links The Sherrill Group – Notes ChemViz Curriculum Support Resources Early ideas in the history of quantum chemistry