First Principles Study Of Transition Metal Compounds

Computational Physics causes more and more physics researchers’ interesting because of its incomparable advantages beyond experimental physics. The first-principles calculation has been used to predicate the physical properties of materials and design materials. In this thesis, I studied the electronic properties of the strongly correlated systems by using the first-principles code BSTATE(Beijing Simulational Tool for Atom Technology).In recent years, transition metal oxides and transition metal fluorides as the strongly correlated electron system have attracted much attention. Research on transition metal oxides started in the fifties and sixties of the last century, the study of this system is mainly concern about its nature of the giant magnetoresistance effect and high-temperature superconductivity. More interesting is that these materials have a wealth of intriguing physical properties, such as metal- insulator transition, charge ordering, orbital ordering, etc., thus become a hot aspect of current physics research. D-shell transition metal elements are not full filled, the transition metal oxide material compose the most of strongly correlated systems, the common feature of these materials is localized 3d or 4d orbits and electron correlation effects is significant. Using first principles calculations we studied the electronic structure, varieties of magnetic, charge ordering state and photon conduction of silver fluorine compounds. In this article we have done the following work:1 By first-principles calculation we studied electronic structure, energy and magnetic moment of different magnetic states(FM, A-AFM, C-AFM and G-AFM) of KAgF3. We using the GGA methods confirmed the ground state is metallic state. Since the 4d orbit of Ag atoms is very localized, so we take the electrons correlation effect into consideration by GGA + U. In the calculation we used U = 4 eV confirmed the ground state is A-type antiferromagnetic insulating state. On this basis, we also calculate the photon conduction, also from the side that is the C-type orbital order.2 By first-principles calculation we studied electronic structure, energy and magnetic moment of different magnetic states(FM, AFM1 and AFM2) of K2AgF4. Taking into account the electrons correlation effect, we adopted GGA + U to confirmed the ground state is AFM2 type antiferromagnetic insulating state. These results can be explained through a variety of energy comparisons and the density of states in different magnetic states.