Mulliken

Mulliken is a surname associated with several individuals, most notably Robert Sanderson Mulliken (1896–1986), an American physicist and chemist who received the Nobel Prize in Chemistry in 1966 for his fundamental work on chemical bonds and the electronic structure of molecules by the molecular orbital method.

In the scientific literature, Mulliken is best known for contributions to molecular orbital theory and the electronic structure of molecules. Mulliken population analysis, named after him, is a method used in quantum chemistry to assign portions of electron density to individual atoms within a molecule. This approach helps chemists interpret bonding and reactivity in terms of atomic contributions.

Mulliken population analysis describes electron density in terms of contributions from basis functions and the overlap populations between atomic orbitals. While widely used, it has limitations, including dependence on the chosen basis set and sometimes producing charges that are not uniquely defined. Alternatives that are commonly employed include natural population analysis (NPA), Hirshfeld charges, and Bader’s atoms-in-molecules schemes.

The legacy of Mulliken’s work is substantial in the field of quantum chemistry. His molecular orbital framework and the population analysis method contributed to a deeper understanding of chemical bonding and have influenced both theoretical developments and practical computational methods used to study molecules today.