Sir Frederick Charles Frank, OBE, FRS (6 March 1911 – 5 April 1998), known as Sir Charles Frank, was a British theoretical physicist. He is best known for his work on crystal dislocations, including (with Thornton Read) the idea of the Frank–Read source of dislocations. He also proposed the cyclol reaction in the mid-1930s, and made many other contributions to solid-state physics, geophysics, and the theory of liquid crystals.
He was born in Durban, South Africa, although his parents returned to England soon afterwards. He was educated at Thetford Grammar School and Ipswich School and went on to study chemistry at Lincoln College, Oxford, gaining a doctorate at the university’s Engineering Laboratory.
Prior to World War II, he worked as a physicist in Berlin and as a colloid chemist in Cambridge. During World War II he joined the Chemical Defence Experimental Station at Porton Down, Wiltshire, but in 1940 was transferred to the Air Ministry’s Assistant Directorate of Intelligence (Science) and spent the rest of the war with the Air Ministry. Due to his work he was made Officer of the Most Excellent Order of the British Empire in 1946.
After the war he moved to the University of Bristol Physics Department to do research in solid state physics, but switched to research on crystal dislocation. His work with William Keith Burton and Nicolás Cabrera was to demonstrate the role dislocations played in the growth of crystals. Apart from crystal defects, his wide-ranging research interests at Bristol included the mechanical properties of polymers, the theory of liquid crystals, the mechanics of the interior of the Earth, and the origin of biological homochirality. He was appointed Reader in 1951, Melville Wills Professor in 1954 and Henry Overton Wills Professor and Director of the H.H. Wills Physics Laboratory in 1969. He retired in 1976 but remained active in attending conferences, writing papers and corresponding with colleagues well into the 1990s. He edited the Farm Hall Transcripts from Operation Epsilon well into his eighties.
In 1963 he won the Fernand Holweck Medal and Prize.
In 1967 he was awarded the A. A. Griffith Medal and Prize. He was also a member of the Materials Science Club Awards Sub-Committee which selected the Griffith medallist for 1972 (L. R. G. Treloar).
In 1994 he was awarded the Royal Society’s Copley Medal, its highest honour, “in recognition of his fundamental contribution to the theory of crystal morphology, in particular to the source of dislocations and their consequences in interfaces and crystal growth; to fundamental understanding of liquid crystals and the concept of disclination; and to the extension of crystallinity concepts to aperiodic crystals.”