John Anthony Pople (born October 31, 1925) is a theoretical chemist. Born in England, he came to the United States of America in the 1950s, where he has resided since then, though retaining British citizenship. He received his B. A. (in 19__) and doctorate (in 1951) degrees in mathematics, from Cambridge University in the United Kingdom. His thesis was, however, on a topic that would generally be considered chemistry: the bonding structures of water. Pople to this day considers himself more of a mathematician than a chemist, but theoretical chemists consider him one of the most important of their number.
His first major contribution was a theory of approximate molecular orbital (MO) calculations on pi electron systems in 1953, identical to the one developed by Rudolph Pariser and Robert G. Parr in the same year, and now called the Pariser-Parr-Pople (PPP) method. Subsequently, he developed the methods of Complete Neglect of Differential Overlap (CNDO) (in 1965) and Intermediate Neglect of Differential Overlap (INDO) (shortly later) for approximate MO calculations on three-dimensional molecules, and other developments in computational chemistry. He pioneered the development of more sophisticated computational methods, so called ab initio methods, that used basis sets of either Slater type orbitals or Gaussian orbitals to model the wave function. While in the early days these calculations were extremely expensive to perform, the advent of high speed microprocessors has made them much more feasible today. He was instrumental in the development of one of the most widely used computational chemistry packages, the "Gaussian(tm)" suite of programs.
In 1986 he moved from Carnegie-Mellon University in Pittsburgh, Pennsylvania, where his earlier accomplishments were made, to Northwestern University in Chicago, Illinois, where he is now a professor.