Dr. Robert J. Le Roy (September 30, 1943 – August 10, 2018) was one of Canada's leading chemists who held the distinguished title of "University Professor" at the University of Waterloo.
Le Roy attended Allenby Public school in North Toronto up to grade 8 and North Toronto Collegiate Institute until 1961. He then received the BSc and MSc degrees from University of Toronto in 1965 and 1967, respectively, and a PhD degree from University of Wisconsin–Madison in 1971.
Le Roy is renowned for two major achievements in the field of chemistry: the development of the Leroy-Bernstein theory, alongside R. B. Bernstein, and the derivation of the LeRoy Radius. Le Roy is also the author of many computer programs that aid in collecting information from experiments. Many of his works are used by schools and labs throughout the world and have contributed to the progress of science.
He was a graduate from the University of Toronto. During his stay there, he began working with theoretical and computational chemical physics, which is what he would deal with for the rest of his career.
In his research, Dr Le Roy used quantum mechanical theory to understand and explain how properties of molecular systems are the results of forces of interaction by quantitatively determining those forces from measurements of various properties.
In almost any area of science, the experimental work ran parallel to the theoretical work and there was constant interplay between the two areas. Dr. Le Roy’s interest was in intermolecular forces. He used quantum mechanics and computer models to define and analyze the basic forces between atoms and molecules. Early in his career, Dr. Le Roy developed a technique for mathematically defining a radius of a small molecule, now known as the Le Roy radius. This established a boundary. Within the boundary, intra-molecular bonding is important, and beyond the boundary, inter-molecular forces predominate. In his work, the study of atomic and molecular spectra (called spectroscopy) played a crucial role. Measurements from spectroscopy help theoreticians develop better models and theories for explaining molecular structure. Computer programs that Dr. Le Roy developed for the purpose of converting experimental evidence to information on forces, shape, and structure are free, and are now routinely used around the world.
It is important not to assume that forces and structures are well established. Our knowledge of bonding and structure becomes more and more scanty and unreliable for larger structures. A huge amount of research remains to be done if we are ever to be able to describe bonding and structure very accurately for even microscopic amounts of complex substances. Dr. Le Roy stated “... except for the simplest systems, our knowledge of (interactions between molecules) is fairly primitive... .” A classic example is our understanding of the structure and activity of proteins—the stuff of life. We know the composition of many proteins quite precisely and the structure can be experimentally determined, but the structure of these large molecules depends on how bonding folds and shapes the chains and branches. How a protein behaves and what it does depends specifically on its precise shape and structure, and that is something scientists often state is “not well understood.”
His work on the Morse/Long-range potential with his former student Nike Dattani of Oxford University was referred to as a "landmark in diatomic spectral analysis" in. In the landmark work, the C3 value for atomic lithium was determined to a higher-precision than any atom's previously measured oscillator strength, by an order of magnitude. This lithium oscillator strength is related to the radiative lifetime of atomic lithium and is used as a benchmark for atomic clocks and measurements of fundamental constants.
Honors and awards 
- 1994 Rutherford Memorial Medal in Chemistry from the Royal Society of Canada
- 1995 J. Heyrovsky Honorary Medal for Merit in the Chemical Sciences from the Academy of Sciences of the Czech Republic.