Molecular Orbital Analysis of Hydrogen Transportation in Perovskite Oxides

Taku Onishi

Mie University, Japan


Chemical bonding rule enables us to judge chemical bonding property of conductive ion. When checking molecular orbitals including outer shell electrons on conductive ion, (1) covalent bonding if formed, if orbital overlap exists between conductive ion and others; (2) ionic bonding is formed, if no orbital overlap exists. For example, in our designed proton conductive aluminium oxide, covalent boding is formed between proton and other atoms. Before starting proton conduction, hydrogen is allocated toward square centre, forming OH covalent bonding. Hydrogen is transported to next neighbouring oxygen, by changing covalent bonding. In addition, it was found that proton pumping effect is combined with the proton conduction. Namely, hydrogen is pumped into square centre, keeping OH covalent bonding, and then chemical bonding change occurs (from OH to OHO). First, our previous results on proton conduction will be introduced. Recently, hydrogen anion conduction was experimentally suggested. However, the mechanism is still unclear. From our calculations, it was found that fluctuation of hydrogen anion occurs within square part. Second, the detailed mechanism on hydrogen anion conduction will be shown. References (1)T. Onishi, Quantum Computational Chemistry-Modelling and Calculation for Functional Materials (Springer Nature), 2018 (2)T. Onishi, Adv. Quant. Chem. 70, 31-67, 2015 (3)T. Onishi, invited talk at ICCMSE 2018