Self-consistent field theory molecular properties

The accurate calculation of these molecular properties requires the use of ab initio methods, which have increased enormously in accuracy and efficiency in the last three decades. Ab initio methods have developed in two directions first, the level of approximation has become increasingly sophisticated and, hence, accurate. The earliest ab initio calculations used the Hartree-Fock/self-consistent field (HF/SCF) methodology, which is the simplest to implement. Subsequently, such methods as Mpller-Plesset perturbation theory, multi-configuration self-consistent field theory (MCSCF) and coupled-cluster (CC) theory have been developed and implemented. Relatively recently, density functional theory (DFT) has become the method of choice since it yields an accuracy much greater than that of HF/SCF while requiring relatively little additional computational effort. 

Various theoretical methods and approaches have been used to model properties and reactivities of metalloporphyrins. They range from the early use of qualitative molecular orbital diagrams (24,25), linear combination of atomic orbitals to yield molecular orbitals (LCAO-MO) calculations (26-30), molecular mechanics (31,32) and semi-empirical methods (33-35), and self-consistent field method (SCF) calculations (36-43) to the methods commonly used nowadays (molecular dynamic simulations (31,44,45), density functional theory (DFT) (35,46-49), Moller-Plesset perturbation theory ( ) (50-53), configuration interaction (Cl) (35,42,54-56), coupled cluster (CC) (57,58), and CASSCF/CASPT2 (59-63)). 

The aim of this chapter is to review the current status of the quantum-mechanical calculation of electric and magnetic properties of isolated atoms and molecules. In view of the rapid advances made during the past decade in the calculation of ab initio molecular wavefunctions, we will clearly concentrate for the most part on the calculation of such properties using standard ab initio methods such as gaussian orbital LCAO-MO-SCF (linear combination of atomic orbital-miolecular orbital-self-consistent field), configuration interaction (Cl), coupled Hartree-Fock, and the like, but will also review similar calculations at the semi-empirical and empirical level where appropriate. For readers unfamiliar with the theory of electric and magnetic properties, the books by Davies and by Atkins review the subject thoroughly, whilst the more technical details of quantum-mechanical calculations on atoms and molecules have been described in many other places. ... 

The present contribution concerns an outline of the response tlieory for the multiconfigurational self-consistent field electronic structure method coupled to molecular mechanics force fields and it gives an overview of the theoretical developments presented in the work by Poulsen et al. [7, 8, 9], The multiconfigurational self-consistent field molecular mechanics (MCSCF/MM) response method has been developed to include third order molecular properties [7, 8, 9], This contribution contains a section that describes the establisment of the energy functional for the situation where a multiconfigurational self-consistent field electronic structure method is coupled to a classical molecular mechanics field. The second section provides the necessary background for forming the fundamental equations within response theory. The third and fourth sections present the linear and quadratic, respectively, response equations for the MCSCF/MM response method. The fifth 283... 

The site-site RISM/HNC theory has been coupled with the ab initio molecular orbital (MO) theory in a self-consistent field (SCF) calculation of the electronic and solvation structure of a solute molecule immersed in molecular solvent, referred to as the RISM-SCF method [59, 60, 61]. Since the site-site treatment of the solute-solvent correlations involves the approximation of radial averaging, it constitutes a bottleneck of the RISM-SCF method. Although this approach yields reasonable results for the thermodynamics of solvation for many solute species and solvents [62], it lacks a 3D picture of the solvation structure for complex solutes and oversimplifies the contribution to the solvation properties from highly directed electron orbitals of the solute molecule. 

A quantitative analysis of counterion localization in a salt-free solution of star-like PEs is carried out on the basis of an exact numerical solution of the corresponding Poisson-Boltzmann (PB) problem (Sect. 5). Here, the conformational degrees of freedom of the flexible branches are accounted for within the Scheutjens-Fleer self-consistent field (SF-SCF) framework. The latter is used to prove and to quantify the applicability of the concept of colloidal charge renormalization to PE stars, that exemplify soft charged colloidal objects. The predictions of analytical and numerical SCF-PB theories are complemented by results of Monte Carlo (MC) and molecular dynamics (MD) simulations. The available experimental data on solution properties of PE star polymers are discussed in the light of theoretical predictions (Sect. 6). 

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