Electronic structure computations complete active-space

In this section, we briefly review the use of the complete active space self-consistent field (CASSCF) method for calculating excited states. This method offers an acceptable compromise between accuracy and computational expense, but our main reason for choosing it is that it offers analytical gradients and second derivatives, which are essential for geometry optimization. As we discuss more fully below, CASSCF is often sufficient if one is interested in structure and mechanism (as we are here), but a more accurate treatment of dynamic electron correlation is often necessary for accurate energetics. 

Basis Sets Correlation Consistent Sets Circular Dichro-ism Electronic Complete Active Space Self-consistent Field (CASSCF) Second-order Perturbation Theory (CASPT2) Configuration Interaction Density Functional Applications Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Electronic Diabatic States Definition, Computation, and Applications ESR Hyperfine Calculations Magnetic Circular Dichroism of rt Systems Non-adiabatic Derivative Couplings Relativistic Theory and Applications Structure Determination by Computer-based Spectrum Interpretation Valence Bond Curve Crossing Models. 

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