“…Two rhombohedral (a and b) and two tetragonal (a and b) structures have been known since the 1950s [1][2][3][4], and the g-phase was recently discovered under high pressure [5]. There has been a lot of research into the properties of a-and b-rhombohedral (a-rh, b-rh) boron, revealing that these materials are p-type semiconductors under normal pressure [6,7].…”