  The theoretical solid-state physicist Walter Kohn was awarded one-half of the
1998 Nobel Prize in Chemistry for his mid-1960's creation of an approach to the
many-particle problem in quantum mechanics called density functional theory
(DFT). In its exact form, DFT establishes that the total charge density of any
system of electrons and nuclei provides all the information needed for a
complete description of that system. This was a breakthrough for the study of
atoms, molecules, gases, liquids, and solids. Before DFT, it was thought that
only the vastly more complicated many-electron wave function was needed for a
complete description of such systems. Today, fifty years after its
introduction, DFT (in one of its approximate forms) is the method of choice
used by most scientists to calculate the physical properties of materials of
all kinds. In this paper, I present a biographical essay of Kohn's educational
experiences and professional career up to and including the creation of DFT.
