Professor Björn O. Roos was a distinguished theoretical chemist and emeritus professor at Lund University in Sweden, where he established himself as a leading authority in quantum chemistry over several decades. Born on June 28, 1937, in Malmö, Sweden, he began his academic journey in the early 1960s as a Ph.D. student, quickly establishing a reputation for rigorous mathematical approaches to chemical problems. Throughout his career, he maintained his primary affiliation with Lund University's Department of Theoretical Chemistry, where he rose to prominence as a professor and mentor. His distinguished service to science earned him membership in the Royal Swedish Academy of Sciences, cementing his status as one of Sweden's most respected theoretical chemists.
Professor Roos made seminal contributions to multiconfigurational quantum chemistry, developing sophisticated computational methods that transformed how scientists approach complex electronic structure problems. His groundbreaking work on the Complete Active Space Self-Consistent Field (CASSCF) method provided researchers with powerful tools to accurately model chemical systems with strong electron correlation effects that were previously intractable. He pioneered approaches for selecting appropriate active spaces in quantum calculations, addressing one of the most challenging aspects of computational chemistry methodology. His influential chapter on Multiconfigurational Quantum Chemistry became a foundational reference for generations of theoretical chemists seeking to understand challenging chemical phenomena.
Throughout his career, Professor Roos maintained an exceptional reputation as a mentor, colleague, and innovator who profoundly shaped the field of theoretical chemistry. He received the prestigious ACS Award in Theoretical Chemistry in recognition of his outstanding contributions to the discipline, highlighting the international impact of his methodological advances. His collaborative spirit is evident in his extensive work with researchers including Roland Lindh, Per Åke Malmqvist, and Valera Veryazov, forming a productive research group that extended his methodologies' reach. Though he passed away on February 22, 2010, in Lund, his theoretical frameworks continue to underpin modern computational chemistry studies worldwide, ensuring his enduring legacy in the scientific community.
