Nikolai Nikolayevich Sirota (born 2.11.1913) — a Soviet physicist, an academician of the Academy of Sciences of the Byelorussian SSR (1956). Born in St Petersburg. He graduated from the Moscow Institute of Steel (1936). In 1941—54 he worked at the Institute of General and Inorganic Chemistry of the USSR Academy of Sciences and at the same time (1945 — 56) at Moscow University. In 1957 — 63 he headed the department of solid-state and semiconductor physics of the Academy of Sciences of the Byelorussian SSR, which was transformed into the Institute of Solid-State and Semiconductor Physics of the Academy of Sciences of the Byelorussian SSR. In 1963 — 74 he was director of this institute, and from 1968 head of a laboratory. In 1957-62 he was also head of a chair at the Byelorussian University, and from 1963 at the Minsk Pedagogical Institute.
His research was in the physics and physical chemistry of solids. He extended the theory of phase transformations other than first-order ones, the theory of the formation of metastable phases in one- and multicomponent systems, and the theory of the polymorphism of simple compounds, and established the factors that give rise to hysteresis in phase transformations. He was the first to study the question of the influence of magnetic and electric fields on the kinetics of crystallisation and of phase transitions. He developed the physical foundations of the tempering of hardened steel. He studied problems of crystal lattice dynamics and its influence on physical properties and on the processes of phase transitions. He developed a number of new materials and a method of obtaining blocks of cubic boron nitride.