Showing papers by "Francesco Mauri published in 2002"
TL;DR: In this paper, a pseudopotential scheme for calculating X-ray absorption near-edge structure (XANES) spectra is presented. But the method is applied to the carbon K edge in diamond and to the silicon and oxygen K edges in $\ensuremath{\alpha}$-quartz for which polarized XANES spectra were measured.
Abstract: We present a reciprocal-space pseudopotential scheme for calculating x-ray absorption near-edge structure (XANES) spectra. The scheme incorporates a recursive method to compute absorption cross section as a continued fraction. The continued fraction formulation of absorption is advantageous in that it permits the treatment of core-hole interaction through large supercells (hundreds of atoms). The method is compared with recently developed Bethe-Salpeter approach. The method is applied to the carbon K edge in diamond and to the silicon and oxygen K edges in $\ensuremath{\alpha}$-quartz for which polarized XANES spectra were measured. Core-hole effects are investigated by varying the size of the supercell, thus leading to information similar to that obtained from cluster size analysis usually performed within multiple scattering calculations.
292 citations
TL;DR: The method is validated by comparison with existing quantum chemical and experimental data for a selection of diatomic radicals and finds the results to be in excellent agreement with experiment for the E(1)(prime) and substitutional phosphorus defect centers in quartz.
Abstract: A theory for the reliable prediction of the EPR $g$ tensor for paramagnetic defects in solids is presented. It is based on density functional theory and on the gauge including projector augmented wave approach to the calculation of all-electron magnetic response. The method is validated by comparison with existing quantum chemical and experimental data for a selection of diatomic radicals. We then perform the first prediction of EPR $g$ tensors in the solid state and find the results to be in excellent agreement with experiment for the ${E}_{1}^{\ensuremath{'}}$ and substitutional phosphorus defect centers in quartz.
138 citations
TL;DR: In this paper, the theoretical infrared spectrum of lizardite [Mg3Si2O5(OH)4] was computed using first-principles quantum mechanical calculations.
Abstract: The theoretical infrared spectrum of lizardite [Mg3Si2O5(OH)4] was computed using first-principles quantum mechanical calculations. Density functional perturbation theory allowed us to derive the low-frequency dielectric tensor of lizardite as a function of the light frequency. The infrared spectrum was then calculated using a model that takes into account the platy shape of particles. A very good agreement was obtained between theory and experiment. This agreement allows us to make an unambiguous assignment of the major absorption bands observed in the IR spectrum of lizardite, including the stretching bands of OH groups.
90 citations
TL;DR: It is shown by experiment and theory that the infrared spectra of chrysotile present multiple ionic-plasmon resonances in the Si-O stretching bands, which are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material.
Abstract: Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of Mg(3)Si(2)O(5)(OH)(4). We show by experiment and theory that the infrared spectra of chrysotile present multiple ionic-plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.
33 citations