Seminars Archive

X-ray absorption spectroscopy and science at extreme conditions: previous results and new opportunities for the XAFS beamline at Elettra

Abstract
Properties of materials are altered, sometimes radically, when very high pressures are applied. The compression offers a route to “breaking down‿ the electronic structure of the atoms themselves, leading to the possibility of creating entirely different bulk properties. For this reason, studies under pressure offer a possibility of experimental verification of different models describing the structural and the electronic properties of matter. The coupling of temperature to pressure is fundamental in Earth science as well as to understand how materials behave in their real environment (e.g. a catalyst at high pressure and temperature). If diffraction methods are still the predominant high pressure techniques for structural studies involving synchrotron radiation, x-ray absorption spectroscopy (XAS) is a powerful probe to study the evolution of the electronic and the local structure in matter as we vary the applied conditions. The sensitivity of XAS to short range order, in addition to its chemical and orbital moment selectivity, make it very complementary to x-ray diffraction in structural characterizations. Some examples of studies at extreme condition of pressure (and temperature) ranging from the field of fundamental physics to Earth science using XAS in dispersive geometry will be highlighted. I will continue showing the results of the first high pressure study performed at the XAFS beamline of Elettra. This concerns the behaviour of GeO2: an archetypal glass forming material for which, with increasing density, the polyamorphism has been observed and a long standing debate is still on-going concerning the evolution of the short and intermediate range order. Future opportunities for the XAFS beamline at Elettra for studies at “extreme conditions‿ will be suggested.