Study On The Structure And Property Of Noble Metal Beryllium Compound By First-principles Calculations

Noble metal compounds with good stability and peculiar electronic structures have broad application prospects in electrocatalysis and thermoelectric materials.This paper systematically studies the crystal structures,thermodynamic stability,kinetic stability,electronic structure and mechanical properties of Be-Ir,Be-Pt and Be-Au systems by global structure search and first-principles calculations.We predicted five new beryllium-iridium compounds,the newly predicted Be Ir,Be₂Ir,Be₃Ir and Be₅Ir are found to be thermodynamically stable at zero pressure,C2/m-Be₇Ir₂found to be thermodynamically stable at 11 GPa.Pnma-Be₂Ir converts into another orthorhombic phase with Imma symmetry at about 22 GPa.With the increase of the Be content,from Be₂Ir to Be₅Ir,the-ICOHP value of the Ir-Be bond gradually decreases,indicating that Ir-Be covalent interaction became weaker.The-ICOHP value of the Ir-Ir bond gradually increases,indicating that Ir-Ir covalent interaction became stronger.Bonding analysis shows the typical multi-center bonds characteristics in Be-rich compounds,including tetrahedral multi-center bonds,triangular bipyramid multi-center bonds,three-center bonds,five-center bonds in twisted Ir Be₄,complex six-center bonds and double Pyramid Eight Center Bonds.Be₂Pt,BePt,Be₃Pt₄,Be₂Pt₃ and BePt₄ are firstly found to be thermodynamically,dynamically and mechanical stable.In addition,Be₂Pt is stable below 17 GPa and Be₂Pt₃ is stable below 70 GPa.The analysis of electronic structure shows that there is a strong hybridization between Be-2p and Pt-5d,indicating a charge transfer can occur from Be-2p to Pt-5d.With the increase of Be content,the electron transfer showed a decreased trend.The results show that the negative oxidation state of Pt can be effectively tuned by controlling Be composition.We have predicted four new Be-Au stoichiometrics（Be₇Au₂,Be Au₃,Be Au₄ and Be Au₅）in the Be-Au system.On the Au-rich side,the structure tends to form a mirror-image structure.In the beryllium-rich side,the structure tends to form a three-dimensional network structure.The electronic structure analysis shows that the Au atom obtains electrons from the Be atom,the electrons are mainly filled in the 6p orbital of Au.In the beryllium-rich side,the Be-Be shows strong multi-center covalent interaction.In the Au-rich side,Be-Au bond holds ionic property and Au-Au shows metal interaction.