ANALYTICAL ENERGY GRADIENTS IN MOLLER-PLESSET PERTURBATION AND QUADRATIC CONFIGURATION-INTERACTION METHODS - THEORY AND APPLICATION

Analytical energy gradients are significant for the routine calculation of many molecular properties. They are important for correlation corrected ab initio methods as they provide the basis for an understanding of the influence of correlation effects on calculated one-electron properties, geometries, and vibrational spectra. The chapter reviews the development of the theory of analytical gradients where the special emphasis is on single-determinant ab initio methods. There are many similarities and relationships among the analytical derivatives for the various methods that can be used to reach a unified theory of analytical derivatives. Further, developments in the area of analytical derivatives are also discussed. The important criterion of ab initio methods to be developed in the future will be the availability and the economy of analytical gradient calculations for these methods can be predicted. © 1992 Academic Press Inc.