The FDMNES program calculates the spectra of different
spectroscopies related to the real or virtual absorption of
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
in material. It gives the absorption cross sections of
photons around the ionization edge, that is in the energy range of
XANES
X-ray absorption near edge structure (XANES), also known as near edge X-ray absorption fine structure (NEXAFS), is a type of absorption spectroscopy that indicates the features in the X-ray absorption spectra ( XAS) of condensed matter due to the ...
. The calculation is performed with all conditions of rectilinear or
circular polarization
In electrodynamics, circular polarization of an electromagnetic wave is a polarization state in which, at each point, the electromagnetic field of the wave has a constant magnitude and is rotating at a constant rate in a plane perpendicular to ...
. In the same way, it calculates the structure factors and intensities of anomalous or resonant diffraction spectra (DAFS or RXS).
The code uses two techniques of monoelectronic calculations. The first one is based on the Finite Difference Method (
FDM) to solve the
Schrödinger equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of th ...
. In that way the shape of the potential is free and in particular avoid the
muffin-tin approximation. The second one uses the Green formalism (
multiple scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
) on a muffin- tin potential. This approach can be less precise but is faster.
FDMNES is used as external program to calculate basic spectra for XANES fitting using
FitIt.
It can also be used to calculate
X-ray Raman scattering X-ray Raman scattering (XRS) is non-resonant inelastic scattering of X-rays from core electrons.
It is analogous to vibrational Raman scattering, which is a widely used tool in optical spectroscopy, with the difference being that the wavelengths ...
spectra.
References
*
External links
FDMNES home page
Physics software
Computational chemistry software
{{chem-software-stub