ACS Award In Theoretical Chemistry

Björn O. Roos, an emeritus professor of theoretical chemistry at Lund University, in Sweden, is being honored for his contributions to quantum chemistry, including the development of new theories to describe the electronic structure of molecules and the efficient integration of these theories into widely distributed computational software.

These new theoretical models dramatically improved the accuracy with which transition-metal-containing compounds and molecular excited states could be characterized, according to Christopher J. Cramer, a professor who studies theoretical chemistry at the University of Minnesota, Minneapolis. Among other applications, Roos’s methods improved the description of reactions involving the simultaneous making and breaking of multiple bonds. They also enabled chemists to account for relativistic effects in theoretical treatments of heavy elements and allowed spectroscopists to predict electronic excitation energies of large molecules and to interpret the spectra of such compounds.

Roos’s work has been “foundational at the most fundamental level,” Cramer says. “Each of his developments has opened some broad new area of chemistry that had hitherto seen little successful theoretical study.” Cramer adds that Roos’s theoretical models “continue to be put to practical use every day in modern calculations and, in many cases, continue to be the benchmark calculations against which new model developments are measured.”

“Björn Roos is the creator of several theoretical methods that have become everyday tools of the working theoretical chemist,” says Donald G. Truhlar, a University of Minnesota professor who studies theoretical and computational chemistry. They include the direct configuration interaction (CI) method, the complete active space self-consistent field (CASSCF) method, and the complete active space second-order perturbation theory (CASPT2) method.

“The methodological developments pioneered by Professor Roos have dramatically and uniquely advanced wave-function theories in quantum chemistry,” Cramer says. “The influence of the direct CI, CASSCF, and CASPT2 models on modern quantum chemistry has been profound, particularly in the degree to which they have permitted the extension of accurate theoretical models to enormous swaths of the periodic table that had been previously inaccessible. This is a testament to the creativity and vision of Professor Roos.”

Roos was born in 1937 in Malmö, Sweden. He earned a bachelor’s degree in physics in 1960 and a Ph.D. in theoretical physics in 1968 at Stockholm University. After a postdoctoral fellowship with Enrico Clementi at IBM Research Laboratory in San Jose, Calif., Roos returned to Stockholm University as an assistant professor in theoretical physics. He became an associate professor in 1972.

He moved to the department of physical chemistry at Lund University in 1977 and was promoted to full professor the following year. He was appointed professor and chair of the university’s newly created department of theoretical chemistry in 1983.

Roos has been a member of the Royal Swedish Academy of Sciences since 1984.