Diatomic Interaction Potential Theory, Volume 1: Fundamentals deals with the theoretical approaches to calculations for diatomic systems in their ground states. More specifically, this book considers the problem of calculating the wave function and energy for the lowest state of a system of N electrons moving in the field of two fixed point charges (the nuclei of a diatomic system) separated by a distance R. Comprised of three chapters, this volume opens with an introduction to the nature of an interatomic interaction potential or potential energy curve. The separation of nuclear from electronic motions is considered, along with the methods used to measure potential energy curves. The next chapter presents a qualitative discussion of potential energy curves, with emphasis on the effects to be expected when two atomic systems are allowed to interact at large separation. The final chapter looks at the main approaches to schemes of calculation: variation theory, perturbation theory, the virial and Hellmann-Feynman theorems, local energy principles, and quantum statistical theories. This monograph will be a useful resource for students and teachers of physical chemistry.