Georgy (Yuri) Viktorovich Wulff (22.06.1863 — 25.12.1925) was a Soviet crystallographer and crystal physicist and a corresponding member of the USSR Academy of Sciences (1921). He was born in Nezhin. He graduated from Warsaw University (1885) and worked there until 1909 (in 1907—08 he was professor at Kazan University). From 1909 he was at Moscow University. In 1911 he left the university in protest against the reactionary actions of Kasso, the minister of education, and moved to the A. L. Shanyavsky People's University. He returned to Moscow University as a professor only after the Great October Socialist Revolution (in 1917).
His main work was in the fields of crystallography, crystal physics, crystal optics, X-ray structural analysis and mineralogy. He proposed a way of deriving all the symmetry classes of crystals and developed a graphical method of handling the results of crystal measurements by means of a stereographic net (the Wulff net). He found (1895) the influence of gravity on the shape of a crystal during its growth from solution, invented a rotating crystalliser and developed a method of obtaining crystals of regular shape. He established the law of the process of crystal growth, according to which the rates of growth of the faces of a crystal are proportional to their specific surface energies (the Wulff law). In 1913, independently of L. Bragg, he derived the conditions for the interference reflection of X-rays by crystals (the Bragg-Wulff formula), which underlie X-ray spectroscopy.
He was the first in Russia to begin X-ray structural studies.