Figure 3

(A) Methane XRD patterns as a function of pressure. Red lines correspond to decomposition at 11.5 GPa and blue lines to decomposition at 29.0 GPa. From 7.3 to 20.7 GPa multiple peaks were indexed to methane’s rhombohedral phase A. At 29.0 GPa a single peak was observed consistent with the simple cubic HP methane phase. (B) Methane molecular volume, obtained from XRD peak positions, as a function of pressure. Methane A and cubic methane equations of state are shown in purple and yellow respectively, with the width of the curve representing uncertainty23. The solid line is the best fitting EOS to the methane A data shown here (P < 25 GPa).