Re-examining the crystal structure behaviour of nitrogen and methane

In the light of NASA's New Horizons mission, the solid-phase behaviour of methane and nitrogen has been re-examined and the thermal expansion coefficients of both materials have been determined over their whole solid temperature range for the first time. Neutron diffraction results indicate that the symmetric Pa (3) over bar space group is the best description for the alpha-nitrogen structure, rather than the long-accepted P2(1)3. Furthermore, it is also observed that beta-nitrogen and methane phase I show changes in texture on warming, indicating grain growth.