Yakov Il'ich Frenkel (Russian: Яков Ильич Френкель) (10 February 1894 – 23 January 1952) was a Soviet physicist renowned for his works in the field of condensed matter physics. He is also known as Jacov Frenkel.
He was born in a Jewish family in Rostov on Don on 10 February 1894. He entered St. Petersburg University in 1910. Frenkel graduated from the university in 3 years and remained there to prepare for a professorship. In 1912 he finished his first work in physics on the earth's magnetic field and atmospheric electricity. This work attracted Abram Ioffe's attention and later turned into collaboration.
From 1921 till the end of his life, Frenkel worked at the Physico-Technical Institute. Beginning in 1922, Frenkel published a book virtually every year. He was the author of the first theoretical course in the Soviet Union. Many students learned physics from these books, in the Soviet Union and abroad. For his distinguished scientific service, he was elected a corresponding member of the USSR Academy of Sciences in 1929.
He married Sara Isakovna Gordin in 1920. They had two sons, Sergei and Viktor (Victor). He served as a visiting professor at the University of Minnesota in the United States for a short period of time in around 1930.
When conducting research on the molecular theory of condensed state, he introduced the notion of the hole. The Frenkel defect became firmly fixed in the physics of solids and liquids. In the 1930s, his research was supplemented with works on the theory of plastic deformation. His theory, now known as the Frenkel–Kontorova–Tomlinson model, is important in the study of dislocations.