Electronic structure and binding mechanism of Cu2O

On-site interband excitations in resonant inelastic x-ray scattering fromCu2O

“…The occupied full and empty densities of states are in broad general agreement with the previous work [41][42][43][44][45][46][47][48][49] although with exception of the semiempirical calculations of Robertson 43 and the selfinteraction corrected local density approximation ͑LDA͒ calculation of Filippetti and Fiorentini, 48 the present calculations reproduce the experimental band gap and valence bandwidth much better than previously ͑Table I͒. In particular, earlier density functional calculations 42,44,46 underestimated the bulk band gap, whereas a Hartree-Fock calculation 45 dramatically overestimated the gap. The failure of these well-established methods is well known and has been discussed in many previous publications.…”

Electronic structure and properties ofCu2O

“…This fact does not permit the use of this methodology for the interpretation of the excitonic spectrum of Cu 2 O, because the band-gap en- ergy is included in all exciton series. The topology and the main features of the band structure agree well with previous calculations 5,7,11,12 except for the aforementioned gap value. The calculated width of the valence band is 7.7 eV, in good agreement with the experimental estimation around 8 eV obtained from the ultraviolet photoelectron spectroscopy ͑UPS͒ experiments reported by Ghijsen et al 8 The calculated total density of states and its orbitalprojected contributions are displayed in The conduction band was studied by Ghijsen et al 8 using bremsstrahlung isochromat spectroscopy ͑BIS͒.…”

“…The three independent components of the elastic tensor were derived numerically from the changes in energy obtained by applying adequate deformations to the unit cell. Good agreement has been obtained for the c 11 and c 12 elastic constants, while there is definite disagreement for c 44 . The present disagreement is certainly to be attributed to the lack of precision of these methods of estimate small values of the elastic constants, as noted previously for cubic zirconia.…”

“…Previous theoretical results for these values are contradictory. The FLAPW band-structure calculations done by Marksteiner, Blaha, and Schwarz 11 give a very large interstitial electron density, reflecting the usual problems of the muffin-tin approaches to determine atomic populations. Ching, Xu, and Wong, 12 with a density-functional method using a basis set of Gaussian functions, obtained a quasineutral description of Cu 2 O with a small negative charge of Ϫ0.07 on the copper atoms.…”

“…7 The works of Ghijsen and co-workers 8,9 and Mariot 10 have been devoted to the study of the x-ray photoelectron spectroscopy ͑XPS͒ spectrum and its comparison with the calculated density of states. Marksteiner, Blaha, and Schwarz, 11 performing full-potential linearized augmented plane wave ͑FLAPW͒ calculations, analyzed the chemical bond in Cu 2 O, focusing on the linear coordination of the copper atoms and discussing mainly the hybridization found for the copper orbitals. More recently, Ching, Xu, and Wong 12 reported a density-functional study of the ground state and optical properties of Cu 2 O. Evarestov and Veryazov 13 have carried out large unit cell-complete neglect 14 indicating that it is unusual, with no strong covalent interactions but with significant deviations from the purely ionic picture.…”