John Edward Lennard-Jones (27.10.1894—1.02.1954) was an English theoretical physicist. He was born in Leigh. He studied at the University of Manchester and in 1924 received his doctorate at the University of Cambridge. From 1925 he was head of the chair of theoretical physics at the University of Bristol and from 1932 head of the chair of theoretical chemistry at Cambridge.
His research concerned atomic physics, the quantum theory of molecular structure, statistical mechanics and quantum chemistry. In 1924 he proposed a semi-empirical formula for interatomic forces and the so-called “Lennard-Jones potential”. He applied quantum mechanics to the study of the structure and the properties of molecules and was a pioneer in quantum chemistry. Together with R. Mulliken and F. Hund he is one of the creators of the theory of molecular orbitals. He was one of the first to use (from 1939) computing machines in quantum-mechanical calculations. His work was also on the study of critical phenomena and on the equation of state of liquids and dense gases. In 1951, using the method of equivalent orbitals, he carried out the first calculations of the ionisation potentials of organic compounds.