Direct modeling of EXAFS spectra from molecular dynamics simulations

A method for generating extended X-ray absorption fine-structure (EXAFS) spectra directly from molecular dynamics trajectories is described. Conventional molecular dynamics trajectories are run, and configurations from the trajectory are saved at periodic intervals. Clusters containing the EXAFS atom at the center are extracted from the configurations and used as input to the multiple scattering code FEFF6, which produces an EXAFS spectrum for each cluster. The separate spectra for the individual clusters are then averaged together to get a configurationally averaged EXAFS spectrum that can be compared directly with experiment. The method is tested on strontium chloride solutions and compared with recent experimental results on strontium nitrate solutions at both standard and supercritical conditions.