b'Point defects in uraniumFirst principles computation yields the effects of magnetic orders and spin-orbit dioxide by density functionalcoupling on the formation of intrinsic defects in Mott insulator uranium dioxide.theory Hubbard model:D efects are critical to thermal and mechanical behavior of nuclear fuel materials, like uranium dioxide, under irradiation. While density functional defect local environment andtheory calculations bring up a method to compute the defect formation occupation matrix control energy from first principles, it is still a technical challenge to model Mott insulators due to complex interplay between Mott physics, magnetic orders, and spin-orbit coupling. The purpose of this project was to develop an efficient computational approach to capture the defect formation energy in strongly correlated Mott insulator uranium dioxide, incorporating both magnetic orders and spin-orbit coupling, and understand the effects of magnetic orders and spin-orbit coupling on the formation of intrinsic defects in uranium dioxide. In fact, intrinsic defects have been computed PROJECT NUMBER:in uranium dioxide using only 1k antiferromagnetic structure without spin-orbit 22P1066-001FP coupling due to the technical difficulty of modeling noncollinear magnetic orders TOTAL APPROVED AMOUNT:and including spin-orbit coupling. In this project, we developed a method based on $205,000 over 2 years f-orbital occupation matrix control to compute the defect formation energy under different magnetic orderings and with spin-orbit coupling, which was applied on five PRINCIPAL INVESTIGATOR:different states, ferromagnetic and 1k antiferromagnetic states without spin-orbit Shuxiang Zhou coupling and FM, 1k antiferromagnetic, and 3k antiferromagnetic states with spin-CO-INVESTIGATOR: orbit coupling, for three different types of intrinsic defects, oxygen vacancy, uranium Chao Jiang, INLvacancy, and oxygen interstitial. For the same type of defect, magnetic orders and spin-orbit coupling are observed to affect the charge and magnetic transition from defect and matrix. Furthermore, the computed defect formation energy and charge state as functions of Fermi levels show the magnetic orders and spin-orbit coupling have non-trivial effects on the formation of intrinsic defects in uranium dioxide.138'