Mikajlo, EA, Dorsett, HE & Ford, M 2004, 'Trends in the band structures of the group-I and -II oxides', Journal Of Chemical Physics, vol. 120, no. 22, pp. 10799-10806.View/Download from: UTS OPUS or Publisher's site
Measured and calculated band structures for the six lightest group-I and -II oxides are reported. Band structures have been measured using electron momentum spectroscopy, a technique that maps the ground-state occupied orbitals resolved both in energy and momentum. Measurements are compared with first-principles calculations carried out within the linear combination of atomic orbitals approximation using both HartreeFock (HF) and density functional (DFT) methods. Three DFT functionals are used representative of the local density approximation, the generalized gradient approximation, and a hybrid method incorporating exact exchange. The calculated O 2p bandwidths and O 2p2s band gaps generally scale linearly with the inverse of the oxygenoxygen separation squared, but consistently show an anomaly at Li2O. These trends, including the anomaly, are also observed in the experimental data. HF calculations consistently overestimate the oxygen 2p2s band gap by almost a factor of two. Measured band gaps lie within the range of the three DFT functionals employed, with evidence that the description of exchange becomes more important as the cation size increases. Both HF and DFT calculations overestimate the oxygen valence bandwidths, with DFT giving more accurate predictions. Both observed and calculated bandwidths converge as the cation size increases, indicating that exchange-correlation effects become less important as the metallic ion becomes larger
Soule, DBBJ, Dorsett, HE & Ford, M 2003, 'The electronic structure of Be and BeO: benchmark EMS measurements and LCAO calculations', Journal Of Physics And Chemistry Of Solids, vol. 64, no. 3, pp. 495-505.View/Download from: UTS OPUS or Publisher's site
The electronic band structures of Be and BeO have been measured by transmission electron momentum spectroscopy (EMS). The low atomic number of beryllium and the use of ultrathin solid films in these experiments reduce the probability of electron multiple scattering within the sample, resulting in very clean `benchmark measurements for the EMS technique. Experimental data are compared to tight-binding (LCAO) electronic structure calculations using HartreeFock , and local density (LDA-VWN), gradient corrected (PBE) and hybrid (PBE0) density functional theory. Overall, DFT calculations reproduce the EMS data for metallic Be reasonably well. PBE predictions for the valence bandwidth of Be are in excellent agreement with EMS data, provided the calculations employ a large basis set augmented with diffuse functions. For BeO, PBE calculations using a moderately sized basis set are in reasonable agreement with experiment, slightly underestimating the valence bandgap and overestimating the O(2s) and O(2p) bandwidths. The calculations also underestimate the EMS intensity of the O(2p) band around the ?-point. Simulation of the effects of multiple scattering in the calculated oxide bandstructures do not explain these systematic differences.
Sashin, VA, Dorsett, HE, Bolorizadeh, MA & Ford, M 2000, 'The Valence Band Structures Of Beo, Mgo, And Cao', Journal Of Chemical Physics, vol. 113, no. 18, pp. 8175-8182.View/Download from: Publisher's site
We have performed direct measurements of the valence band structures of the light alkaline earth oxides BeO, MgO, and CaO using electron momentum spectroscopy (EMS). From these measurements, we have determined the band dispersions, valence bandwidths, and O(2s)-O(2p) intervalence bandgaps at the Gamma point. For comparison we have also performed Hartree-Fock (HF) and density-functional (DFT) calculations in the linear combination of atomic orbitals (LCAO) approximation. Intervalence bandgaps compare reasonably well with the DFT calculations and previous experimental and theoretical studies. Our measured bandwidths, however, are significantly smaller. In particular, we find that contrary to conventional wisdom, the local density approximation of DFT overestimates the valence bandwidths of these ionic solids. (C) 2000 American Institute of Physics. [S0021-9606(00)70642-8].