The fourth volume of the Collected Works is devoted to Wigners
contribution to physical chemistry, statistical mechanics and
solid-state physics. One corner stone was his introduction of what is
now called the Wigner function, while his paper on adiabatic
perturbations foreshadowed later work on Berry phases. Although few in
number, Wigners articles on solid-state physics laid the foundations for
the modern theory of the electronic structure of metals.