Two quantum chemists whose work helped make computational studies of molecules an everyday activity for scientists were awarded the Nobel Prize in Chemistry today. Walter Kohn of the University of California, Santa Barbara, and John Pople of Northwestern University in Evanston, Illinois, were lauded for developing computational quantum chemistry, which allows scientists to study the inner workings of molecules and better understand chemical reactions.
Since the development of quantum mechanics in the 1920s, chemists have longed to use this fundamental theory describing the behavior of atoms and their electrons to quantify and predict chemical reactions. But for decades, equations generated by quantum laws had been too difficult to solve for molecules, which involve multiple atoms and swarms of electrons. Thanks to the work of Kohn and Pople, "this is no longer a pipe dream," says Henry Schaefer, a quantum chemist at the University of Georgia in Athens.
Kohn, a Vienna-born physicist, became a central figure in the development of "density functional theory" in the mid 1960s. He helped simplify quantum chemical calculations by showing that the computations don't need to keep track of every electron; instead, it's enough to calculate the density of electrons at each point around a molecule. This quantity dictates much of the molecule's personality, including the shapes it can assume and the kinds of reactions it can engage in. For his part, Pople, a British citizen, also developed new computational methods for quantum chemistry and designed a computer program which allows researchers to study molecular structures and properties. "The key is to make the view [of the molecule] from the outside simple and direct," says Pople, who learned of his good fortune over a hotel breakfast in Houston.
With such powerful and easy-to-use tools, quantum chemistry has infiltrated the chemistry community and beyond. "In many ways, quantum chemistry has become a black box procedure that anyone can use," says Mark Ratner, a colleague of Pople's at Northwestern. Says Ratner: "That's why atmospheric scientists, astrophysicists, geologists, and even neurologists are using it."