RMC – Reverse Monte Carlo Analysis

The analysis of EXAFS spectra of highly disordered materials is difficult in general because the signal is strongly damped and the amplitude of the signal is low, leaving a low signal to noise ratio and a formidable problem for the removal of the background. An elegant treatment of this problem is RMC modeling which was first applied to the analysis of EXAFS spectra of amorphous and crystalline silicon and AgBr by Gurman and McGreevy. Originally, it was developed by McGreevy and Pusztai for the analysis of neutron scattering data of liquids. The RMC algorithm is based on the computation of the complete EXAFS spectrum from the partial radial distribution functions generated from atomic configurations. The unfiltered EXAFS signal containing the complete experimental information is analysed in k-space by Reverse Monte Carlo (RMC) analysis with the newly developed program ‘rmcxas’. Theoretical amplitude and phase functions are calculated by ‘feff’. Radius dependent (curved wave) phase and amplitude functions are used.