Local s, p and d charge distributions and X-ray emission bands of SiO₂: alpha -quartz and stishovite

Abstract

Aktml. An experimental and theoretical study of the electronic structure and the x-ray Si K and Si L emission bands of 42aoordinated @ q u a m and 63-coordinated slishovite is presented. The nature of atomic states participating in the x-ray valence band spectra is idcntified. In particular the longstanding controversy a b u t the mle of Si M-like states is analysed; evidently, Si M-like electrons essentially contribute 10 the intensity of Si L emission bands We have calculated the total density of states, the local partial densities of states. the ratios of the s, p and d charge componenls inside silicon and mygen Sited spheres, and the Si K and Si L minion bands. mere is good agreement behveen our measured and alculated spectra. Reasons are given why in contrast with the Si K emission bands the Si L emission bands are inxwitive to the local c y t a l stmcture of aquam and stishovite.

The bond character of rutile type SiO2, GeO2 and SnO2 investigated by molecular orbital calculation

“…The role played by d-orbitals in Si± ±O bond formation is a controversial problem (Gibbs, Downs, Boisen, 1994, Simunek, Vackar, Wiech, 1993. The electron emission spectra about a-quartz and stishovite have been analyzed by Wiech (1984).…”

“…The electron emission spectra about a-quartz and stishovite have been analyzed by Wiech (1984). Simunek et al (1993) have concluded that Si 3d-orbital does not participate in the Si± ±O bond. The Si K-and Si L-emission bands reflect the Si p-like and Si s/d-like electrons of the valence band, respectively.…”

Structural changes induced by lattice–electron interactions: SiO2stishovite and FeTiO3ilmenite

“…The bonding electrons observed from X-ray diffraction study are interpreted by the optimized pair potential and molecular orbital calculation (Svane & Antoncik, 1987;Mimaki et al, 2000). The electron orbital overlapping and the bonding energy render the deformation of MO 6 octahedra of rutile-type structures from the bond character (Baur & Khan, 1971;Simunek et al, 1993;Camargo et al, 1996;Gibbs et al, 1997Gibbs et al, , 1998. The structure change with pressure is characterized by the molecular orbital overlapping with the metal-metal interaction.…”

Investigation of an Mo/SiO2 interface by electron-induced x-ray emission spectroscopy

“…This is typical of SiO 2 13,15 and in agreement with local and partial Si 3p state calculations of SiO 2 . 16,17 When decreasing the excitation energy, i.e. when probing silica thicknesses closer to the interface with Mo, changes are seen towards higher photon energies: the intensity of the structures increases, leading to a shift and a broadening of the spectral density.…”

“…At 3 keV, when the entire SiO 2 layer is analysed, the O 2p density is characteristic of silica 12 and in agreement with the theoretical density of states. 16,17 The band has its maximum at 526.9 eV and is asymmetrical towards the lower photon energies. The structure at ¾521.7 eV is due to the second-order Na K˛emission coming from surface contamination.…”