Re-examining the crystal structure behaviour of nitrogen and methane.

In the light of NASA's 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 3 space group is the best description for the α-nitrogen structure, rather than the long-accepted 23. Furthermore, it is also observed that β-nitrogen and methane phase I show changes in texture on warming, indicating grain growth.