First-principles Study Of Iridium Oxide Under High Pressure

Transition metal oxides are widely used in the frontier fields of production and life,among which platinum group metals are widely used in aerospace and other cuttingedge technologies due to their advantages of high melting point,high strength and stable chemical properties.With the development of materials science,the research of transition metal oxides under high pressure is becoming more and more thorough.In recent years,the discovery of high temperature superconducting oxides,topological Mott insulators and Weyl semi-metals has stimulated the enthusiasm of scholars in this field,hoping to provide theoretical support for the design of functional materials by studying transition metals under high pressure.Iridium oxide is one of the most concerned materials,because it is an excellent catalyst for oxygen evolution reaction.Previous articles focused more on the research of reaction mechanism and thin film materials and less on the physical mechanism of material system.The current studies on iridium oxide under high pressure are all in the pressure range of less than 100 GPa,and no studies on ultra-high pressure are involved.The latest study uses ab initio method to theoretically simulate the structure and lattice dynamics of Iridium dioxide under high pressure conditions of 60 GPa.In order to further expand the high-pressure phase diagram of iridium oxides,we studied iridium oxygen system compounds in the high-pressure range of 300 GPa.By regulating the pressure,we hope to discover the properties of the materials in the system,thus contributing to the development of materials science.By calculating the thermodynamic enthalpy value,we first determined that the stable structure in the system was iridium oxide,and compared it with the structure of iridium oxygen compound in the published paper and calculated the formation energy,and found that our phase diagram was more accurate.Secondly,by calculating the elastic constants of energy strain combined with stress strain,it is found that the toughness of iridium oxide can be increased by pressure.The corresponding Debye temperature is calculated by elastic constants.It is found that the first two terms of Debye temperature decrease with pressure,and the third term increases with pressure.The phonon scattering diagram and the high temperature and high pressure phase diagram under quasi-harmonic approximation provide strong evidence for the phase transition process of the system,and prove that the three structures of iridium oxide are stable under high pressure.By calculating the material’s energy band,Fermi surface state density,projected orbit state density and Fermi surface filling parameters,it is found that all three phases of the material are metallic phases,and the material has antimetallization phenomenon through the change of Fermi surface filling parameters.