High Quality Content by WIKIPEDIA articles! Elemental boron can exist in four allotropic forms: rhombohedral ?-boron; rhombohedral ?-boron; orthorhombic ?-boron; and tetragonal ?-boron (also known as T-192, or T-boron). Although at least 14 more allotropes have been reported, these other forms are based on tenuous evidence, or are stable only at elevated pressures, or are thought to represent boron frameworks stabilized by impurities. Whereas the ? phase is the most stable and the others are metastable, the transformation rate is negligible at room temperature, and thus all four phases can exist at ambient conditions. Boron can also be prepared in two amorphous forms: one having the appearance of a brown powder; the other an opaque, black glassy solid. Amorphous brown boron and polycrystalline rhombohedral ?-boron are the most common forms. Данное издание представляет собой компиляцию сведений, находящихся в свободном доступе в среде Интернет в целом, и в информационном сетевом...