Structural transformations in liquid, crystalline, and glassy BO under high pressure

Brazhkin, V. V.*; Katayama, Yoshinori; Inamura, Yasuhiro; Kondrin, M. V.*; Lyapin, A. G.*; Popova, S. V.*; Voloshin, R. N.*

We present in situ (X-ray diffraction) and ex situ (quenching) structural studies of crystalline, liquid, and glassy BO up to 9 GPa and 1700 K, drawing equilibrium and nonequilibrium phase diagrams of BO, Particularly, we have determined the melting curve, the stability regions for crystalline BO and BO II modifications, the regions of transformations, such as densification or crystallization, for both the liquid and glassy states, including the region of sharp first-order-like transition in liquid BO to a high-density phase near 7 GPa. Quenching experiments also show that the transition to the high-density liquid can occur at much lower pressures in nonstoichiometric melts with an excess of boron. BO is the first glassformer whose transformations in the disordered state have been comparatively studied for both liquid and glassy phases.