ABSTRACT
Great progress in computational techniques and methods in the last decade of the 20th century has made it possible to perform quantum mechanical (QM) calculations on large molecular systems composed of several dozens or even hundreds of atoms. General ab initio schemes based on Hartree-Fock-Roothaan (HFR) methods [1], formerly used for small molecules composed of light elements, now are becoming applicable for metal complexes, including even heavy metals. Calculations based on the density-functional theory [2] have appeared particularly fruitful in this respect. These methods have also been applied in solvent extraction chemistry. Reviews have been presented, e.g., [3,4], on the computational methods-from purely empirical molecular mechanics (MM) approaches to advanced ab initio calculations rendered accessible in the form of commercial software packages: Cerius2 [5], Gaussian 98 [6], ADF [7], Spartan [8], HyperChem [9], etc. These methods and programs have been widely used for structural optimization of metal complexes and calculation of their energy of formation, problems of primary importance in solvent extraction.
