Author: Hans Boysen

Abstract
Any model of the structure and dynamics of the Earth’s interior does not only require a profound knowledge of the crystallographic structures and textures of the various constituents under actual high temperature and high pressure conditions, but also that of their thermodynamic properties. Inelastic (INS) and (incoherent) quasielasic (QNS) neutron scattering studies are indispensable tools to determine the lattice dynamics, phase transitions, diffusion properties and melting behaviour of these materials. From the phonon density of states and the phonon dispersion curves essential thermodynamic parameters like specific heat, equation of state, lattice expansion, elastic constants, anomalies near structural phase transitions and the melting point, and interatomic potentials can be obtained. With the latter it is possible to theoretically explore the entire spectrum of thermal vibrations under various temperature and pressure conditions. QNS allows investigating the diffusion behaviour, of particular importance that of hydrogen, including glasses and liquids. In this contribution a brief general introduction will be presented and illustrated by examples of the high temperature phase transitions in quartz, leucite and enstatite, important minerals of the Earth’s crust and upper mantle, respectively.

Author Description
Sektion Kristallographie, Department für Geo- und Umweltwissenschaften, Ludwig-Maximilians Universität München, Theresienstr. 41, D-80333 München