Simple molecular solids become unstable at high pressures, typically transforming to dense framework and/or metallic structures. We report formation of an unusual ionic solid NO(+)NO(3)(-) (nitrosonium nitrate) from N(2)O at pressures above 20 GPa and temperatures above 1000 K. Synchrotron x-ray diffraction indicates that the compound crystallizes with a structure related to the aragonite form of CaCO(3) and NaNO(3). Raman and infrared spectroscopic data indicate that the structure is noncentrosymmetric and exhibits a strong pressure dependent charge transfer and orientational order.

In this study a commercial evacuated tube solar hotwater system was modified to be used as a thermal-power source for a thermodynamic engine. Commercial hot-water systems are meant to operate at temperatures that are close to the boiling point of water. Single-tube non-imaging concentrators were built in order to increase the input solar-radiation per tube and therefore supply thermal-power at temperatures of 180 − 220 • C. Simulations and experiments show that it is possible to use concentrators to increase the temperature range of thermal power extracted from a commercial evacuated tube system and use this modified system to increase the efficiency of solar-thermal energy generation.