La 0.7A' 0.3MnO 3 catalysts by MS- Xα and CNDO/2 methods

Abstract

This paper presents the orbital energies and the densities of states near the Fermi level of the pero Vskite type catalysts La 0.7A' 0.3MnO (A' = Sr, Ba, Ca), calculated by the MS- Xα method. It compares the frontier orbital electronegativities of the catalysts to those of the adsorbed molecules (O 2 and CO). This work also includes the total energy curves of the catalyst model with the adsorbed molecules calculated by the CNDO/2 method, compares the relative strength of adsorption of both O 2 and CO, and discusses the catalytic mechanism of the oxidation of CO. It is promising that the noble-metal catalysts used in the oxidation of CO for purification of automobile exhausts and for other purposes could be replaced by the peroVskite type catalysts La 0.7A' 0.3MnO 3 (A' = Sr, Ba, Ca). The catalysts, which are very active in such an oxidation reaction, have been studied for years by many authors, and considerable headway has been made experimentally. Theoretically, however, interpretation of the catalytic mechanism in terms of molecular interactions has not been available. This paper presents some theoretical results of the adsorption and activity of the catalysts studied by the MS- Xα and CNDO/2 methods.