Dresden 2014 – wissenschaftliches Programm

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KR: Fachgruppe Kristallographie

KR 8: Poster Crystallography

KR 8.2: Poster

Mittwoch, 2. April 2014, 17:00–19:30, P4

Using an innovative Vinet EoS approximation for parametric refinement of high pressure powder diffraction data — •Martin Etter and Robert E. Dinnebier — Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany

The relationship between the thermodynamic state variables pressure, volume and temperature can normally be described with so-called equation of states (EoS), which are semi-empirical determined and which are often used with an isothermal description. Among this semi-empirical EoS, the Vinet EoS is believed to be the most accurate, allowing to describe the behavior of most material systems under high pressure up to a compression of 40%. Similar to other EoS like the Birch-Murnaghan EoS or the natural strain EoS, the Vinet EoS has an pressure on volume dependency, which makes it unsuitable for parametric refinement of high pressure powder diffraction data, where the pressure is the independent variable and the volume is the dependent which is a refineable quantity. Using an innovative Taylor series expansion of the Vinet EoS, it is possible to obtain an equation which is analytical invertible and therefore useful for a direct parametric refinement in analysis programs like TOPAS. By means of high pressure powder diffraction data of different material systems the validity of the newly developed EoS is evaluated and demonstrated.