High-(P,T) properties of tantalum and titanium carbides and nitrides

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We propose to study the structural response of TiC1-xNx (0 < x < 1) and the Ta-analogues to high (P,T) conditions by neutron diffraction experiments employing heatable¿ Paris-Edinburgh¿-type cells and quantum mechanical molecular dynamics simulations. Thermodynamic properties, including the melting behaviour, will be obtained by laser-heated diamond anvil cell experiments. Melting temperatures as a function of (P,T) will be obtained by visual in situ observation, while other thermodynamic properties will be derived from ex situ x-ray diffraction. Laser heated diamond anvil cell experiments will also be used to explore the possibility of inducing a self-propagating high-temperature synthesis (SHS) at high pressures. A successful demonstration of a SHS in a DAC would have important implications for high temperature studies of refractory compounds and would help to establish the use of a laser-heated DAC as a reaction chamber at extreme conditions. The determination of the structural response to high (P,T)-conditions from the neutron diffraction experiments would be used to evaluate the applicability of quantum mechanical MD to such extreme conditions, and would contribute to a deeper understanding of fundamental crystal chemical relations for a very large family of compounds