Photoelectron and Optical Spectra Derived from Self‐Consistent Charge MO and Band Calculations for Bulk and Surface of BaTiO3

Abstract

AbstractBoth MO and band structure calculations are performed for the cubic phase of BaTiO3 based on a self‐consistent charge procedure following the semi‐empirical Cusachs scheme. The photoelectron spectra derived from the MO calculations are considerably cluster dependent. The experimental XPS valence band (VB) spectrum is well represented by the band structure calculations for the bulk. Comparing band structure calculations for three hypothetical thin films of BaTiO3 with experimental UPS VB results from the preceding paper of Courths it is concluded (i) that the surface of BaTiO3 consists of a TiO2 layer, and (ii) that the experimental UPS VB spectra may be interpreted in terms of contributions from the surface TiO2 layer plus those from the inner BaO and TiO2 layers. Calculated optical transitions in the range 0 to 15 eV are in rough agreement with experimental reflectivity spectra of Bäuerle et al. and Cardona. The calculations show that selfconsistency has significant effects on ionization and Madelung potentials and therefore on the electronic structure of BaTiO3.