This project examines how the advent of quantum mechanics shaped theoretical research in solid-state/condensed matter physics. From an electron theory essentially confined to the empirical, the new quantum mechanical framework allowed physicists to make quantitative predictions about actual materials (without experiment), if only the necessary tools and algorithms were available. Some physicists began to work towards the goal of a fundamental, quantum-mechanical description of real materials that would be free of empirical parameters. This work led eventually to what is emerging today as Computational Material Science.

We study how leading theorists viewed the basic theoretical concepts of the solid state as they emerged, and we examine how groups of physicists used the new theory differently. Some worked towards qualitative, sometimes intuitive model-based descriptions of complex phenomena in solids; others performed increasingly precise model-based calculations and worked towards a material-specific, predictive description of basic quantities: energy band structure, defect properties, and others. The use of advanced computational means was crucial to these efforts. We trace how the use of new computational resources (even in the 1930s) was intertwined with new conceptual developments in theoretical physics, helping to usher in new – often contested - standards of theoretical precision, but also sparking specialization and divisions among the growing post-war cadres of computing physicists.

Finally, we examine how changed computational resources and a broadened understanding of “computation,” from after the war up to the present, helped shape, change and refine key physical concepts in solid state/condensed matter research. One example is the advent of density functional theory. A conceptual approach that initially seemed like a leap of faith in the context of Thomas-Fermi theory and Slater’s X-alpha approach, it was later proved to be exact in principle for all ground state observables, enabling increasingly trustworthy quantitative computations of materials properties based on quantum-mechanical principles alone.