He laid the foundations of band structure calculations of metals and semiconductors, culminating in the discovery of the Orthogonalized Plane Wave Method (O.P.W.). He was years ahead of his time in this contribution. A great deal of modern solid state physics as produced today stems from this original and early paper.
His influence on the development of solid state physics extends to a deep understanding of many facets such as surface physics, of thermionic emission, of transport phenomena in semiconductors and of collective excitations in solids such as spin waves.
He created the theoretical physics division at Bell Telephone Laboratory. Because of this, the total research effort at this institution and brought about much of the most original research in condensed matter physics during the last 30 years.
He has also been most influential in promoting international cooperation among scientists and through his character and his personal example, he has exemplified a somewhat unattainable ideal of how a research scholar in any field should operate.
He has contributed to religion and science discussions. He has stated about God that "Things such as truth, goodness, even happiness, are achievable by virtue of a force that is always present, in the here and now and available to me personally".