Sir Frederick Charles Frank (1911–1998), known almost universally as Charles Frank, was one of the most versatile and intuitive theoretical physicists of the 20th century. A polymath of the "Bristol School," Frank possessed a singular ability to visualize complex three-dimensional structures, allowing him to solve fundamental problems in fields as diverse as metallurgy, crystal growth, polymer science, and geophysics.
1. Biography: From Durban to Bristol
Early Life and Education
Born on March 6, 1911, in Durban, South Africa, Frank moved to England with his parents at the age of ten. He was educated at Thetford Grammar School before entering Lincoln College, Oxford. He initially studied chemistry, earning his undergraduate degree in 1933, but his interests quickly pivoted toward the physical underpinnings of matter. He completed his D.Phil. in 1937, partially conducting research at the Kaiser Wilhelm Institute in Berlin under the legendary Peter Debye.
The "Wizard War" Years
During World War II, Frank’s career took a detour into scientific intelligence. He joined the Air Ministry, working under R.V. Jones. Frank played a pivotal role in the "Battle of the Beams," deciphering the radio navigation systems used by the Luftwaffe to guide bombers. His ability to deduce the technical specifications of German radar and V-weapons from fragmentary data made him a key figure in British wartime intelligence.
The Bristol Era
In 1946, Frank joined the University of Bristol at the invitation of Nevill Mott (later a Nobel Laureate). He remained at Bristol for the rest of his career, serving as the Henry Overton Wills Professor of Physics and eventually as the Director of the H.H. Wills Physics Laboratory. He was knighted in 1977 for his contributions to science.
2. Major Contributions
Frank’s work was characterized by "geometrical intuition." He looked at how atoms arranged themselves and how those arrangements broke or shifted.
- Crystal Growth and the Screw Dislocation: Before Frank, physicists couldn't explain why crystals grew as fast as they did; theoretical models suggested they should grow much slower. In 1949, Frank realized that crystals are rarely perfect. He proposed that "screw dislocations" (spiraling defects in the atomic lattice) provide a permanent "step" on the surface where new atoms can easily attach. This revolutionized crystallography.
- The Frank-Read Source: Collaborating with Thornton Read, he identified the mechanism by which dislocations multiply when a metal is stressed. This "Frank-Read Source" explains why metals can be deformed (ductility) without shattering, a cornerstone of modern metallurgy and materials science.
- Liquid Crystals (Frank Free Energy): Frank developed the foundational continuum theory for liquid crystals. He identified three types of deformation—splay, twist, and bend—and formulated the "Frank Free Energy" equation, which remains the standard for calculating how liquid crystal molecules respond to electric fields (the basis for LCD technology).
- Frank-Kasper Phases: He identified complex structures in metallic alloys where atoms are arranged in high-coordination polyhedra. These "Frank-Kasper phases" later became essential in the study of quasicrystals.
- Polymer Morphology: He was a pioneer in understanding how long-chain molecules fold. He described the "shish-kebab" structure in polymers, where crystals grow linearly along a central thread.
3. Notable Publications
- "The influence of dislocations on crystal growth" (1949): Published in Discussions of the Faraday Society, this paper solved the long-standing mystery of crystal growth rates.
- "Multiplication processes for slow moving dislocations" (1950): Co-authored with W.T. Read in Physical Review, introducing the Frank-Read source.
- "On the theory of liquid crystals" (1958): Published in Discussions of the Faraday Society, this is the most cited paper in the history of liquid crystal research.
- "The theory of crystal growth" (1951): A seminal book (co-authored with Burton and Cabrera) that remains a primary reference in the field.
4. Awards & Recognition
Frank’s accolades reflect his standing as a "scientist's scientist":
- Fellow of the Royal Society (1954): Elected for his work on crystal defects.
- Knight Bachelor (1977): For services to science.
- The Royal Medal (1979): Awarded by the Royal Society for his original contributions to the theory of crystal growth and plastic deformation.
- The Copley Medal (1994): The Royal Society’s oldest and most prestigious award, previously won by Einstein and Darwin.
- A.F. Kapustinsky Medal: Recognizing his contributions to crystallography.
5. Impact & Legacy
Charles Frank’s legacy is embedded in the physical objects of the modern world. Every time a structural engineer calculates the fatigue of a steel beam, or a consumer looks at an LCD smartphone screen, they are utilizing principles Frank first described.
He is credited with transforming "materials science" from a collection of empirical observations into a rigorous, predictive mathematical discipline. His work on the physics of the Earth's interior—specifically mantle convection—also influenced the early development of plate tectonics theory.
6. Collaborations
- Nevill Mott: Their partnership turned Bristol into a global hub for solid-state physics.
- Thornton Read: His collaborator at Bell Labs during the development of dislocation theory.
- R.V. Jones: His mentor in wartime intelligence, with whom he shared a lifelong friendship and a penchant for "lateral thinking."
- The Bristol Polymer Group: He mentored Andrew Keller, who became a world leader in polymer science.
7. Lesser-Known Facts
- The "Frank" Style: Frank was known for his brevity and piercing questions. In seminars, he would often sit with his eyes closed, appearing to sleep, only to wake at the end and ask a question that exposed a fundamental flaw in the speaker’s logic.
- Cold Fusion Skeptic: In 1989, when "cold fusion" was announced, Frank was one of the first to provide a sober theoretical analysis (specifically regarding muon-catalyzed fusion), helping the scientific community separate hype from reality.
- Diamond Expert: He was fascinated by diamonds and spent years studying their growth and the "trigons" (triangular pits) found on their surfaces. He became a consultant for De Beers, applying his crystal growth theories to the industrial production of diamonds.
- A "Visual" Thinker: Colleagues noted that Frank rarely used complex algebra to start a problem. Instead, he would "see" the geometry of the atoms in his mind and then find the mathematics to describe what he was seeing.