Erwin Madelung (18.05.1881-1972) was a German theoretical physicist. He was born in Bonn. In 1905 he received the degree of Doctor of Philosophy at the University of Göttingen, where he was a privatdozent in 1905 — 12. From 1919 he was professor at the University of Kiel, from 1920 at the University of Münster, and in 1920 — 50 professor at the University of Frankfurt and director of the Institute of Theoretical Physics (FRG).
His work was in the field of solid-state physics and mathematical physics. He established the connection between the elastic constants of a crystal and the frequencies of vibration of its atoms. He discovered (1909) quantitative relations between the elasticity and the natural (optical) frequency of diatomic compounds. He studied the structure of ionic crystals. He proved (1910) that ions occupy the sites of the crystal lattice of common salt. The Madelung constant is associated with his name.