GNXAS: A SOFTWARE PACKAGE FOR ADVANCED EXAFS MULTIPLE-SCATTERING CALCULATIONS AND DATA-ANALYSIS

Abstract

Computational and theoretical advances for the interpretation of the x-ray absorption spectroscopy (XAS) cross-section, and associated extended x-ray absorption file structure (EXAFS), originally published in Phys. Rev. B 52, 15122 and 15135, (1995), are at the basis of an advanced software package for EXAFS data analysis, denominated GNXAS. This software package is composed of a series FORTRAN programs for EXAFS data-analysis (including the main codes crymol, phagen, gnpeak, gnxas, and fitheo) together with several utility programs for sample optimization, automatic background subtraction, and edge analysis. The GNXAS package allows scientists to perform accurate multiple-scattering EXAFS calculations of the XAS cross-section achieving a reliable refinement of the structural models in the short-range. These characteristics are useful to take full advantage of the high data quality obtained at modern synchrotron radiation facilities. The philosophy, methodology, and practical usage aspects of the main data-analysis codes are described in details in this paper. The procedures for the estimation of statistical errors and for the data analysis of liquid and highly disordered systems are also discussed. A useful list of references on the development of the method and applications to various scientific fields is included. The content of this paper can be regarded as a full documentation and guide for proper usage of the current version of the GNXAS software.