THE LOW-TEMPERATURE PHASE-TRANSITIONS IN SOLID CH4-CD4 MIXTURES .2. THE ABSENCE OF THE II-III-PHASE TRANSITION AT X BETWEEN 0.05 AND 0.15

The low temperature phase transitions in a (1 - x)CH4 - xCD4 mixture for x = 0.125 have been investigated by means of proton spin-lattice relaxation time measurements up to 700 bar. The II-III transition as it occurs in the pure substances was not found in the mixture at this CD4 concentration. Instead, another transition to a low temperature phase was found. Once this phase is produced at a pressure above 500 bar it can be maintained down to zero pressure. The experimental results indicate that this low temperature phase is metastable. Spin conversion in this mixture was observed as an increase of the proton relaxation time below 8 K. © 1990.