Peter Debye

Peter Joseph William Debye was born Petrus Debije in Maastricht in 1884. He studied at Aachen and then Munich, taking his doctorate under Arnold Sommerfeld, who called Debye his most important discovery. Over a long career he held chairs at Zurich, Utrecht, Göttingen, Leipzig and Berlin before emigrating to the United States in 1940 and settling at Cornell University.

In 1912 Debye produced the model of specific heats that bears his name. Where Einstein's 1907 quantum theory of solids assumed every atom vibrated at a single frequency, Debye treated the lattice vibrations as a whole spectrum of elastic waves up to a maximum frequency. His model correctly reproduced the experimental fact that the heat capacity of a solid falls toward zero as the cube of the temperature near absolute zero, and it introduced the Debye temperature as the characteristic scale of a solid's vibrations.

Debye's range was extraordinary. He explained the temperature dependence of dielectric constants through molecular dipole moments (the debye unit of dipole moment is named for him), developed with Erich Hückel the theory of strong electrolytes, and pioneered the use of X-ray and electron diffraction from powders to determine molecular structure. He was awarded the Nobel Prize in Chemistry in 1936 for these contributions to the study of molecular structure.

Debye left Germany in 1940 rather than take German citizenship as demanded, and spent the rest of his career at Cornell, where he turned to light-scattering studies of polymers. He became a US citizen and died in Ithaca, New York, in 1966.