Contents:

  • Robert Laskowski A New Program for Radical Tessellation Construction and Analysis   abstract | full text
  • Grzegorz Bergmański, Jarosław Rybicki and Giorgio Mancini A New Programme Package for Structural Analysis of Computer Simulated Solids   abstract | full text
  • Adriano Filipponi and Andrea Di Cicco GNXAS: a software package for advanced EXAFS multiple-scattering calculations and data-analysis   abstract | full text

Abstracts:

hRobert Laskowski A New Program for Radical Tessellation Construction and Analysis

The purpose of this work is to describe usage of computer program SIMPL designed for construction and analysis of radical tessellations of any computer simulated sample. The radical polyhedra (RP) [Gellatly B J and Finney J L 1982 J. Non-Cryst. Solids 50 313] can be considered as a generalization of the Voronoi polyhedra more widely used in literature. RP is a minimal polyhedron whose faces are sets of such points that distances from the points to tangent points of two neighboring atomic spheres are equal. The tessellation technique is a very efective tool for structural analysis of computer simulated samples, giving a great amount of easily accessible information. SIMPL allows to construct RP network for defined system and analyze shape, composition and mutual geometrical relation of radical polyhedra and radical simplices. Implemented capabilities give, for example, the posibility to recognize atomic environments' shape and investigate the non-local order in computer simulated materials. The pattern recognition technique [Laskowski R et al. 1997 TASK Quart. 1 96] is based on analysis of the shape of the radical polyhedra, and contraction of short edges and small faces of the polyhedra. Non-local order analysis involves geometric relations between tessellation simplices.

 

hGrzegorz Bergmański, Jarosław Rybicki and Giorgio Mancini A New Programme Package for Structural Analysis of Computer Simulated Solids

The opportunity to gain detailed information on representative set of rings and chains of atoms is of great importance in the analysis of medium-range order in the computer simulated structures of solids. In the paper, a new program package (ANELLI) for ring and chain analysis of computer simulated atomic structures is presented. The paper includes detailed description of input and output files. The package presentation is followed by exemplary results obtained using our programs.

 

hAdriano Filipponi and Andrea Di Cicco GNXAS: a software package for advanced EXAFS multiple-scattering calculations and data-analysis

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.

 

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