Compressibility and Melting Curve of Adamentane to 20 Kbar

The compressibility of adamantane was measured to 20 kbar at 20°C. The solid-solid transition occurs at this temperature at 4.1 kbar with a volume change of 1.8 cm3/mole. The melting curve of adamantane rises with pressure with an initial slope of 25.6°C/kbar, but shows considerable curvature at higher pressures. The triple point tetragonal/fee/liquid can be expected near 460°C, 27, kbar. The volume of activation for self-diffusion in adamantane is estimated at 75 cm3/mole by using Nachtrieb's T/Tm law.