TOPOLOGY AND QUANTUM THEORY OF ATOMS IN MOLECULES AND CRYSTALS R. F. W. Bader, Department of Chemistry, McMaster University, Hamilton Ont. L8s 4M1, Canada

The topological definition of an atom in a molecule is extended to generalize the defintion of a Wigner-Seitz cell in a solid. The topological definition of molecular structure identifies all the atomic interactions that determine a crystal structure, the identification providing a firm physcial basis for a new crystal classification scheme and for establishing structure-property relationships. The identification of the atoms in a crystal with proper open systems enables one to define their conributions to all of the properties of a crystal and to determine the local properties of specific micro-structures such as defects and surface adsorption sites.