High-pressure and high-temperature phases of nitrous oxide

The phase diagram of nitrous oxide (N$_{2}$O) is investigated up to 50 GPa and 1000 K using first principles theory. The calculated stability and properties of numerous crystalline structures are compared with experimental results. We identify the structure of phase II of N$_{2}$O. On the basis of its stability with respect to orthorhombic deformations, an explanation for measured Raman spectra is provided. Similarly to CO$_{2 }$[1], crystalline structures with bent molecules are found to be extremely unfavorable energetically. \newline \newline [1] Bonev et al., Phys. Rev. Lett. 91, 065501 (2003).