Corner rounding of crystals growing at high pressure

The benzene crystal growing at high pressure was visually observed using the optical liquid high pressure cell. The octahedral single crystals, surrounded by {111} faces of the orthorhombic lattice, were observed. The sharp corners in the particular direction abruptly rounded beyond a critical temperature that depended on pressure and concentration. Such pressure, temperature and concentration dependence of the corner shape was observed for the first time. It is possible that the corner rounding originates from the effect of surface free energy, and the transition-like change of the corner shape arises from the thermal roughening transition of the minor singular face at the corners.