Software


RFit2000

RFIT2000 fits X-ray and neutron reflectivity data. The search of global minima is done via successive descent from local minima. This method can be treated as a two stage loop repeated consequently. The first stage is the local minimization with the ?2 -like criterion and the second one is the descent from the most recent local minimum. Reflectivity curve is calculated with one of the methods: Kinematic, Parratt and Matrix. Matrix method works faster for films modeled with multiple repetion of one identcal structural units. Film structure is represented with the box model. Each box is characterized with the scattering density (Re and Im), thickness and roughness of the top interface.

ROD

ROD is a program that can be used to do a refinement of a surface structure using surface X-ray diffraction data. All main features one encounters on surfaces, like roughness, relaxations, reconstructions and multiple domains, are taken into account. The most essential part of ROD is the calculation of the structure factor of the surface. ROD is complemented by two utilities: ANA and AVE: ANA can be used to integrate scans and to convert these into structure factors, while AVE can sort and average data, determine agreement factors and produce a data file for the program ROD.

SASfit

SASfit has been written for analyzing and plotting small angle scattering data. It can calculate integral structural parameters like radius of gyration, scattering invariant, Porod constant. Furthermore it can fit size distributions together with several form factors including different structure factors. Additionally an algorithm has been implemented, which allows to simultaneously fit several scattering curves with a common set of (global) parameters. This last option is especially important in contrast variation experiments or measurements with polarised neutrons. The global fit helps to determine fit parameters unambiguously which by analyzing a single curve would be otherwise strongly correlated.

SasView

SasView is a Small Angle Scattering (SAS) analysis package for the analysis of 1D and 2D scattering data directly in inverse space. The focus was originally on neutron data (SANS) but has been used for X-ray’s as well and includes a tool for determining a slit resolution for the SAXSess instrument. SansView also includes PrView to invert SAS data to P(r), a resolution calculator, and a scattering length density calculator among others tools. A simple plugin mechanism is available for users to add custom models.

SPR-KKR

The SPRKKR band structure package allows to calculate the electronic structure of arbitrary 3-D periodic systems, including systems with chemical disorder. The treatment of 2-D periodic systems (e.g. surfaces) can be done at the moment only by using an auxiliary system having three dimensional periodicity or by making use of the cluster approximation. The electronic structure calculation can be done in a non-relativistic, scalar-relativistic as well as fully relativistic mode. In the scalar-relativistic mode paramagnetic as well as spin-polarized systems can be treated, including non-collinear spin structures and arbitrary spin spirals. In the fully relativistic mode, paramagnetic as well as spin-polarized systems with an arbitrary spin configuration can be dealt with. On the basis of the electronic structure calculation, many different properties can be investigated with a strong emphasize on response functions and spectroscopic properties.

Unscrambler X

Commercial software product for multivariate data analysis, used for calibration of multivariate data which is often in the application of analytical data such as near infrared spectroscopy and Raman spectroscopy, and development of predictive models for use in spectroscopic analysis of materials. Unscrambler X was an early adaptation of the use of partial least squares (PLS). Other techniques supported include principal component analysis (PCA), 3-way PLS, multivariate curve resolution, design of experiments, supervised classification, unsupervised classification and cluster analysis.

VASP

VASP is an ab initio simulation package based on DFT. It is used for atomic scale materials modelling, e.g. electronic structure calculations and quantum-mechanical molecular dynamics from first principles. VASP computes an approximate solution to the many-body Schrödinger equation, either within density functional theory (DFT), solving the Kohn-Sham equations, or within the Hartree-Fock (HF) approximation, solving the Roothaan equations. Hybrid functionals that mix the Hartree-Fock approach with DFT are implemented as well. Furthermore, Green's functions methods (GW quasiparticles, and ACFDT-RPA) and many-body perturbation theory (2nd-order Møller-Plesset) are available. Central quantities, like the one-electron orbitals, the electronic charge density, and the local potential are expressed in plane wave basis sets. The interactions between the electrons and ions are described using norm-conserving or ultrasoft pseudopotentials, or the projector-augmented-wave method. To determine the electronic ground state, VASP makes use of efficient iterative matrix diagonalisation techniques, like the residual minimisation method with direct inversion of the iterative subspace (RMM-DIIS) or blocked Davidson algorithms. These are coupled to highly efficient Broyden and Pulay density mixing schemes to speed up the self-consistency cycle.

WIEN2k

The program package WIEN2k allows to perform electronic structure calculations of solids using density functional theory (DFT). It is based on the full-potential (linearized) augmented plane-wave ((L)APW) + local orbitals (lo) method, one among the most accurate schemes for band structure calculations. WIEN2k is an all-electron scheme including relativistic effects.

XOP (includes SHADOWVUI)

XOP (X-ray Oriented Programs) is a widget-based driver program used as a common front-end interface for modelling of x-ray sources characteristics of optical devices (mirror, filters, crystals, multilayers, etc.); multipurpose data visualizations and analyses

XRMC

XRMC is a Monte Carlo program for accurate simulation of X-ray imaging and spectroscopy experiments in heterogeneous samples. The use of the Monte Carlo method makes the code suitable for the detailed simulation of complex experiments on generic samples. Variance reduction techniques are used for reducing considerably the computation time compared to general purpose Monte Carlo programs. The program is written in C++ and has been tested on Linux, Mac OS X and MS Windows platforms. XRMC is released under the terms of the GPLv3.