High pressure-high temperature phase diagram of ammonia.
The high pressure (P)-high temperature (T) phase diagram of solid ammonia has been investigated using diamond anvil cell and resistive heating techniques. The III-IV transition line has been determined up to 20 GPa and 500 K both on compression and decompression paths. No discontinuity is observed at the expected location for the III-IV-V triple point. The melting line has been determined by visual observations of the fluid-solid equilibrium up to 9 GPa and 900 K. The experimental data are well fitted by a Simon-Glatzel equation in the covered P-T range. These transition lines and their extrapolations are compared to the reported ab initio calculations.
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Institut de Minéralogie et de Physique des Milieux Condensés, Département Physique des Milieux Denses, CNRS UMR 7590, Université Pierre et Marie Curie-Paris VI, Paris Cedex 05, France. sandra.ninet@impmc.jussieu.fr
Datchi
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