hide
Free keywords:
Absorption spectra; Amorphous carbon; Amorphous films; Calculations; Carbides; Chemical bonds; Chromium; Coordination reactions; Extended X ray absorption fine structure spectroscopy; Light absorption; Nanocomposite films; Nanocomposites; Stochastic systems; Thin films; Transition metals; X ray absorption; X ray absorption near edge structure spectroscopy, Comparison with measurements; Computationally efficient; Experimental spectra; Extended Xray absorption fine structure (EXAFS) spectroscopies; First-principles calculation; Nanocomposite thin films; Transition metal carbide; X-ray absorption near-edge structure, Amorphous materials
Abstract:
The local structure and chemical bonding in two-phase amorphous Cr1-xCx nanocomposite thin films are investigated by Cr K-edge (1s) X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies in comparison to theory. By utilizing the computationally efficient stochastic quenching (SQ) technique, we reveal the complexity of different Cr-sites in the transition metal carbides, highlighting the need for large scale averaging to obtain theoretical XANES and EXAFS spectra for comparison with measurements. As shown in this work, it is advantageous to use ab initio theory as an assessment to correctly model and fit experimental spectra and investigate the trends of bond lengths and coordination numbers in complex amorphous materials. With sufficient total carbon content (≥30 at. ), we find that the short-range coordination in the amorphous carbide phase exhibit similarities to that of a Cr7C3 ± y structure, while excessive carbons assemble in the amorphous carbon phase. © 2016 American Chemical Society.
