Publication

Microscopic origin of concentration fluctuations over intermediate range distances in network-forming disordered systems

Alfredo Pasquarello
2007
Journal Articles

Abstract

Ab initio molecular dynamics simulations of liquid GeSe2 show that the first sharp diffraction peak in the concentration-concentration structure factor S-CC(k) is due to a sequence of connected fourfold rings. These subunits can be viewed as chains of edge-sharing tetrahedra. Ge atoms at the opposite tails of these chains are mostly miscoordinated and separated from each other by intermediate range distances. This result correlates a specific structural subunit to a subtle intermediate range order property, involving both the structural and chemical composition of the disordered network.

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https://infoscience.epfl.ch/entities/publication/31030b3b-c4e4-40f1-8f10-c536fe6d2328

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Alfredo Pasquarello
2007
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/31030b3b-c4e4-40f1-8f10-c536fe6d2328

About this result

Related concepts (28)

Powder diffraction

Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials. An instrument dedicated to performing such powder measurements is called a powder diffractometer. Powder diffraction stands in contrast to single crystal diffraction techniques, which work best with a single, well-ordered crystal. Diffraction grating The most common type of powder diffraction is with x-rays, the focus of this article although some aspects of neutron powder diffraction are mentioned.

Neutron diffraction

Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of the structure of the material. The technique is similar to X-ray diffraction but due to their different scattering properties, neutrons and X-rays provide complementary information: X-Rays are suited for superficial analysis, strong x-rays from synchrotron radiation are suited for shallow depths or thin specimens, while neutrons having high penetration depth are suited for bulk samples.

X-ray crystallography

X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information.

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Microscopic origin of concentration fluctuations over intermediate range distances in network-forming disordered systems

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