The nature of the transition from supercooled liquid metal Si to the disordered solid phase, with possible implications for B

The melting of crystalline silicon is well known to result in a metallic liquid. But when this is supercooled, it leads to a 'glass' transition to a non-metallic solid. This prompts us to first propose that in this 'metastable' phase transition the driving mechanism is the Coulomb repulsion between the electrons, the atomic structure remaining largely intact across the transition. This proposal then leads us to draw attention to the likely interest of the now very complex bonding in crystalline boron. Again, as with the simple sp3 bonding in Si, melting produces a metallic liquid in which supercooling is possible and for which earlier diffraction studies have proved possible using levitation techniques. It will be of interest to determine experimentally whether a glassy state exists for B, as single-component glasses are rare, only Si and S being known currently from diffraction experiments.