Molecules in Magnetic Fields

Abstract

<p>This thesis is primarily an investigation of those properties of closed-shell molecules which result from interaction with an external magnetic field. Throughout, emphasis is placed on the observable, magnetically induced current density distributions. The insistence that measurable magnetic response properties such as the NMR shielding tensors and diamagnetic susceptibility tensors be interpreted, physically, in terms of the corresponding induced current distribution has led to new, and more accurate, methods of predicting these properties. These methods are described in Chapter 1. The fundamental features of the induced vector current fields are investigated in Chapter 2 through a formal topological analysis of divergenceless three-dimensional vector field with magnetic symmetry together with actual analyses of several induced molecular current distributions. In chapter 3 the experimentally measurable molecular magnetic susceptibility and nuclear magnetic shielding tensors are analyzed in terms of the corresponding tensors for atoms in molecules to address the physical basis for the empirical models which have been developed to explain experimental results. An atomic magnetic response tensor is entirely determined by the charge and induced current density distributions within the atom and on its surface. The physical significance of the atoms of theory is reiterated through the agreement of the theoretical group magnetic susceptibilities in the hydrocarbons with the empirically defined group increments of Pascal. In chapter 4, advances in methods of calculating properties of atoms in molecules are described.</p>