John C. Slater - Atoms, Molecules and Solids: Research Preceding World War II

Atoms, Molecules and Solids: Research Preceding World War II

Returning in time to 1920, Slater had gone to Harvard to work for a Ph.D. with Percy Bridgman, who studied the behaviour of substances under very high pressures. Slater measured the compressibility of common salt and ten other alkali halides—compounds of lithium, sodium, potassium and rubidium, with fluorine, chlorine and bromine. He described the results as "exactly in accord with Bohr's recent views of the relation between electron structure and the periodic table". This brought Slater's observation concerning the mechanical properties of ionic crystals into line with the theory that Bohr had based on the spectroscopy of gaseous elements. He wrote the alkali halide paper in 1923, having "by the summer of 1922" been "thoroughly indoctrinated ... with quantum theory", in part by the courses of Edwin Kemble following a fascination with Bohr's work during his undergraduate days. In 1924, Slater went to Europe on a Harvard Sheldon Fellowship. After a brief stay at the University of Cambridge, he went on to the University of Copenhagen, where "he explained to Bohr and Kramers his idea (that was) a sort of forerunner of the duality principle, (hence) the celebrated paper" on the work that others dubbed the Bohr-Kramers-Slater (BKS) theory. "Slater suddenly became an internationally known name.". Slater discusses his early life through the trip to Europe in a transcribed interview.

Slater joined the Harvard faculty on his return from Europe in 1925, then moved to MIT in 1930. His research papers covered many topics. A year by year selection, up to his switch to work relating to radar includes:

• 1924: the theoretical part of his Ph.D. work, the Bohr-Kramers-Slater (BKS) theory,
• 1925: widths of spectral lines; ideas that came very close to the electron spins principle,
• 1926 and 1927: explicit attention to electron spin, and to the Schrödinger equation;
• 1928: the Hartree self-consistent field, the Rydberg formula,
• 1929: the determinantal expression for an antisymmetric wave function,
• 1930: Slater type orbitals (STOs) and atomic shielding constants,
• 1931: linear combination of atomic orbitals,; van der Waals forces (with Jack Kirkwood, as a Chemistry Research Associate).
• 1932 to 1935: atomic orbitals, metallic conduction, application of the Thomas–Fermi method to metals,
• 1936: ferromagnetism, (with Erik Rudberg, later Chairman of the Nobel Prize committee for Physics) inelastic scattering, and (with his Ph.D. student William Shockley and close to his own Ph.D. topic), optical properties of alkali halides
• 1937 and 1938: augmented plane waves, superconductivity, ferromagnetism, electrodynamics,
• 1939 he published "only" a book: the definitive Introduction to Chemical Physics,
• 1940 the Grüneisen constant, and the Curie point,
• 1941 phase transition analogous to ferromagnetism in potassium dihydrogen phosphate.

In his memoir, Morse wrote "In addition to other notable papers ... on ... Hartree's self-consistent field, the quantum mechanical derivation of the Rydberg constant, and the best values of atomic shielding constants, he wrote a seminal paper on directing valency " (what became known, later, as linear combination of atomic orbitals). In further comments, John Van Vleck pays particular attention to (1) the 1925 study of the spectra of hydrogen and ionized helium, that J.V.V. considers one sentence short of proposing electron spin (which would have led to sharing a Nobel prize), and (2) what J.V.V. regards as Slater's greatest paper, that introduced the mathematical object now called the Slater determinant. "These were some of the achievements (that led to his) election to the National Academy ... at ... thirty-one. He played a key role in lifting American theoretical physics to high international standing." Slater's doctoral students, during this time, included Nathan Rosen Ph.D. in 1932 for a theoretical study of the hydrogen molecule, and William Shockley Ph.D. 1936 for an energy band structure of sodium chloride, who later received a Nobel Prize for the discovery of the transistor.