John C. Slater was born on December 22, 1900 to an academic family (his dad was the head of the English department at the University of Rochester. As a boy, John enjoyed working with things that were electrical, mechanical and chemical. However, it wasn't until later in his life that the word "physics" was applied to his interest by a tutor. This moment was the point that decided the career little John would follow--a career as an American phycist. In following this path, John was a major contributor to the new world of quantum mechanics.

When John was enrolled at the University of Rochester, he took courses in physics, mathematics, and chemistry. After graduating in 1920, he was off to Havard for graduate school, where he had the opportunity to study classical physics under P.W. Bridgeman. It was also while he was at Havard that he was introduced to the new quantum physics of E.C. Kemble. This influence was so powerful that colleague J.H. VanVleck recalls, "by Summer of 1922, he was indoctrinated in the successes and failures of the then quantum theory [now referred to as the crisis of quantum theory.] After obtaining his Ph.D., John was off to Europe to study. He eventually landed in Coppenhagen in 1922, where he worked with N. H. D. Bohr. There he explained to Bohr and Kramer his idea that classical radiation field guided light quanta, which a forerunner of the duality principle. The result was the paper "The Quantum Theory of Radiation" with Bohr and Kramer. It was this paper that made John an internationally known figure.

In 1924, John returned to Harvard as an instructor and assistant professor. By 1926, he was compiling the physical and physico-chemical properties of atoms, molecules, and solids from the basic equations of quantum mechanics. In 1929, John wrote what some consider to be "his greatest paper"---"The Theory of Complex Spectra." This paper introduced Slater determinants, Slater F and G parameters. Also in 1929, John was appointed to the head of the MIT physics department. He promptly began to format a plan to revise the physics curriculum so that the U.S. could catch up to the standards set in Europe. At approximately this time, his research interests shifted from atomic structure to molecular and solid state structure, producing many "groundbreaking papers." During the 1940s, John turned to defense research by working in the Radiation Laboratory on the development of radar. Later, he transferred to the Bell Telephone Laboratories to do work on the theory of the magnetron and magnetron design. After the war, his interests returned to molecular and solid state physics. In 1950, he organized and directed a small research group called Solid State and Molecular Theory Group (SSMTG). In 1951, he left MIT for Brookhaven National Laboratory on Long Island. The University of Rochester awarded John, and his 92 year-old father, honorary degrees. In 1965, John took a position at the University of Florida (because their retirement age was higher) where he joined the Quantum Theory Project. He died on July 25, 1976 at the age of 76.

The body of Slater's works are extensive and contain the following topics: the compressibilities of solids, the magnetic properties of ferromagnetic and antiferromagnet materials, the bonding energies and magnetic properties of various polyatomic molecules, X-ray absorption in molecules and solids, the relationship between Xa method and the virial theorem, dispersion theory, spectroscopic transition probabilities, interpretation of spectra, radiation theory, and the application of quantum mechanics to chemical, spectroscopic, magnetic, and other properties of atoms, molecules and solids.

However, Slater's most commonly recognized works among quantum students are Slater determinants, Slater orbital, Slater-type orbitals, and F and G integrals. Slater determinants are wavefunctions satifying the Pauli e principle written in determinant form. The Pauli principle states that the total wavefunction must be antisymmetric with respect to the interchange of any pair of electrons, which results in the Pauli exclusion principle, where no two electrons occupy the same state. Thus, the electrons are paired into spin up and spin down. This pairing is incorporated into the wavefuction of the Slater determinant. Slater orbitals introduced specifications for approximations to atomic orbitals. Slater type orbitals are Slater orbitals scaled up or down in size. These atomic orbitals help to approximate the actual wavefunction. Finally, F and G integrals are integrals describing the energies of all the states arising for a given configuration, while the interconfiguration interaction is ignored.

John published many, many papers and books during his career. Here I focus on one of his articles, "Cohesion in Monovalent Metals." First, John lays the groundwork necessary to understand his paper. By examining the lowest state of a metal, information about the electric and magnetic properties of the metal can be obtained. During a comparison of Heizenberg's and Bloch's methods and a discussion of the hydrogen molecule, he introduces the relationship between the valence bond method and the molecular-orbital method and finds that they yield the same results. He then uses the results to investigate the electronic structure of a metal and its cohesive, elecric, and magnetic properties. He begins with non-polar states, disregards exchange integrals except between adjacent atoms and a linear lattice with n atoms uniformily spaced along a line. The task is to compute the matrix of the energy with respect to the wave functions and then solve the problem of making the proper linear combinations. The development of the matrix "is simple." The diagonal components are a sum of the energies of the separate atoms (not considered here); the sum over all the adjacent pairs, as the pair of atoms a and b, of integrals J(a/b); and the sum over all adjacent pairs which have the same spin. All nondiagonal terms are zero, with the exception of those where the distributions in the two states differ only the the exchange of an adjacent a and b. In these cases, the term is -K. The solution of the linear equations for the S's is the "real problem." There are two methods of approximation, one for large spins and the other for small spins. First, large spins with all the spins parallel is discussed. Since a linear lattice is being considered, there are (n-1) adjacent pairs and all the spins are parallel, causing the energy to be (n-1)J-(n-1)K. This is a positive term resulting in a repulsive term. In teh case n_{a}= n-1 and n_{b}=1, the energy levels are evenly distributed between the values W(0) = (n-1)J-(n-3-2cosp(n-1)/n) K= (n-1)J-n-5)K. For two electron of spin b, the distribution in energy of the terms can be found about the value (n-1)J-(n-1-2n_{b})K. Using methods such as these, estimates of the polar states depressing teh nonpolar one can be made. Next, a space distribution of zero spin is considered. Using a body-centered cubic lattice, a perturbed energy of 4nJ + (4nK^{2}/14K) = 4nJ + (2/7)nK is obtained. Finally, the equations are tested using the sodium crystal. The results were in qualitative agreeement with the experimental values.

ReferencesLowdin, Per-Olov, Ed.;

Quantum Theory of Atoms, Molecules, and the Solid State: A Tribute to John Slater;Academic Press, New York: 1966.

Biographical Memoirs; National Academy of Sciences, vol. 53, National Academy Press, Washington, D.C.: 1982.Slater, J.C.;

Solid-State and Molecular Theory: A Scientific Biography;John Wiley & Sons, New York: 1975.