Computational photochemistry states

The BOVB method does not of course aim to compete with the standard ab initio methods. BOVB has its specific domain. It serves as an interface between the quantitative rigor of today s capabilities and the traditional qualitative matrix of concepts of chemistry. As such, it has been mainly devised as a tool for computing diabatic states, with applications to chemical dynamics, chemical reactivity with the VB correlation diagrams, photochemistry, resonance concepts in organic chemistry, reaction mechanisms, and more generally all cases where a valence bond reading of the wave function or the properties of one particular VB structure are desirable in order to understand better the nature of an electronic state. The method has passed its first tests of credibility and is now facing a wide field of future applications. 

Merchan M, Serrano-Andres L (2005) Ab Initio Methods for Excited States. In Olivucci M (ed) Computational Photochemistry, Elsevier, Amsterdam. 

Selected theoretical and computational photochemistry references.135 136 136 Ground-state Molecular Oxygen... 

M. Merchan and L. Serrano-Andres, Ab initio methods for excited states, in J. Michl, M. Olivucci (Eds.), Computational photochemistry, Elsevier, Amsterdam, 2004. 

A fundamental theoretical issue for computational photochemistry is the treatment of the hop (nonadiabatic) event. One needs to add the time propagation of the solutions of the time-dependent Schrodinger equation for electronic motion to the classical propagation of the nuclei, thus obtaining the populations of each adiabatic state. The time-dependent wave function for electronic motion is just a time-dependent configuration interaction vector ... 

The very nature of the photochemical processes the multi-state multiconfigurational character and the occurrence of non-adiabatic behavior -leads to the fact that the field of computational photochemistry is still far from saturated with respect to computational tools and method developments. The need to treat several excited states, of different electronic character (covalent, ionic, charge-transfer, Rydberg, etc.), without bias requires the applied theory to be developed at a rather high level of sophistication. While TD-DFT to a large extent is attractable for Born-Oppenheimer molecular dynamics and trajectory surface hopping (TSH), due to its speed, it has its limitations in what type of transitions are correctly... 

Classical Dynamics of Nonequilibrium Processes in Fluids Integrating the Classical Equations of Motion Control of Microworld Chemical and Physical Processes Mixed Quantum-Classical Methods Multiphoton Excitation Non-adiabatic Derivative Couplings Photochemistry Rates of Chemical Reactions Reactive Scattering of Polyatomic Molecules Spectroscopy Computational Methods State to State Reactive Scattering Statistical Adiabatic Channel Models Time-dependent Multiconfigurational Hartree Method Trajectory Simulations of Molecular Collisions Classical Treatment Transition State Theory Unimolecular Reaction Dynamics Valence Bond Curve Crossing Models Vibrational Energy Level Calculations Vibronic Dynamics in Polyatomic Molecules Wave Packets. 

The electronic structure method used to provide the energies and gradients of the states is crucial in photochemistry and photophysics. Ab initio electronic structure methods have been used for many years. Treating closed shell systems in their ground state is a problem that, in many cases, can now be solved routinely by chemists using standardized methods and computer packages. In order to obtain quantitative results, electron correlation (also referred to as dynamical correlation) should be included in the model and there are many methods available for doing this based on either variational or perturbation principles [41],... 

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