ELNES spectroscopy and XANES calculations of the OKedge: Orientation dependence and effects of protons inMg(OH)2

Abstract

In this study, it is demonstrated that high-resolution orientation-dependent electron energy-loss near-edge fine structure recorded in a transmission electron microscope provides key information on the effect of protons on the O K edge of ${\mathrm{Mg}(\mathrm{OH})}_{2}$ (brucite). The contribution of protons to the O K edge has been identified on the basis of theoretical simulations and interpretations of the x-ray-absorption near-edge structure, which has been modeled in the framework of full multiple scattering theory and the tight-binding linear muffin-tin orbital band-structure method. The orientation-dependent experimental data agree well with theoretical calculations, taking into account the structural anisotropy. The O-H bonds parallel to the c axis produce two characteristic peaks at 10 and 20 eV above the onset of the O K edge when momentum transfer is parallel to c. The O K-edge spectrum is interpreted in terms of mixing between the central O p and neighboring H $1s$ and Mg $3s$ and $3p$ orbitals.