sp~3/sp~2 characterization of carbon materials from first-principles calculations: X-ray photoelectron versus high energy electron energy-loss spectroscopy techniques

摘要

We have performed X-ray photoelectron spectroscopy (XPS) and high energy electron energy-loss spectroscopy (HEELS) calculations from first principles on a series of Monte Carlo generated amorphous carbon materials and have used a technique which separates the n* and sigma* components of the energy-loss near-edge structure spectra of carbon materials on the basis of the ab initio electronic structure calculations of graphite to determine the sp~3 fraction of the carbon systems. While the XPS technique is found to probe the local coordination geometry, the sp~3 fractions resulting from the HEELS technique are found to be in very good agreement with those based on the pi-orbital axis vector analysis which accounts for the effects of non-planarity in 3-coordinated systems.