The Crystal Structure And Electronic Structure Of Ir-Ta Binary Oxide

Ta2O5-IrO2 active oxide system has been discussed in this paper by ab initio density functional theory method.(1)The structure of intrinsic rutile type IrO2 and ?-Ta2O5 are calculated by density functional theory method.(2)The structure of rutile Ir1-xTaxO2 is optimized to obtain the structure parameter and the total energy of ground state,and the influence of doping amount on electronic structure of Ir1-xTaxO2 has been discussed.(3)The structure of ?-Ta1-xIrxO2.5 is optimized to obtain the structure parameter and the total energy of ground state,and the influence of doping amount on electronic structure of Ir1-xTaxO2 has been discussed.The results suggested that:(1)The crystal parameters of rulite IrO2 that calculated by GGA(generalized gradient approximation)is more close to the JCPDS card than LDA(local density approximation).The parameters of(3-Ta2O5 is close to the experiment,too.The band structure shows that intrinsic rutile type lrO2 has metallic properties,while(3-Ta2O5 is direct band gap semiconductor and the forbidden band width is 0.212 eV.The electronic density of states show that the peaks of density of states at the Fermi level of intrinsic rutile type IrO2 are mainly composed of O 2p electronic states and Ir 5d electronic states,while those of ?-Ta2O5are mainly composed of O 2p electronic states and Ta 5d electronic states.(2)The crystal volume of rutile Ir1-xTaxO2 that calculated with GGA increases with the doping amount of Ta.The formation energy of different ratio of doping all above zero,suggests that the Ir-Ta-O solid solution is easy to separate,when Ta doped into rutile IrO2.O-O and Me-Me average bond length increase as the doping amount increasing,so they are considered to represent the structure of rutile Ir1-xTaxO2.The energy band structure shows that adding a small amount Ta can improve electrical conductivity of solid solution.The density of states suggest that with the doped impurity level introduced,interactions of Ta 5d electronic state and O 2p electronic state are improved.Bader charge shows the enhancement ionic of Ta-O,the weakness covalent of Ir-O,and the trend are approximately.(3)Computing the crystal parameters and volume of Ta1-xIrO2.5 solid solution,we find that its change rule along with the doping amount completely off the line.The formation energy suggests that Ta1-xIrxO2.5 solid solution is easy to decompose and more likely to form a disorderly phase.The result of bond length calculation shows:the change trend of Me-Me bond length and V-x curve are similar,so it can be used to represent the structure of characteristic.Band structures show that the conductivity of solid solution will change semiconductor-semimetal-metal with the increasing of Ir.Density of states figure shows that the doped Ir-Ta-O solid solution is affected by 5d electronic state,producing p-d hybridorbital,which enhance the interactions of Ir 5d and O 2p.Net charge ratio Ta:O and Ir:O increases with x,and Ta-O ionic has subsided,Ir-O covalent enhancement.Charge density figures show that there is different shape charge area around Ir,forming the effective orbital overlap,enhancing the electrical conductivity.