The crystal structure of a simple rhombohedral form of boron

摘要: A new modification of boron, resulting from the pyrolytic decomposition of BI z on a heated surface (800 C. to 1100 C.), has been found to have a simple rhombohedral structure, with a 0= 5.057/~ and c~= 58.06, space group R3m, Z----12. The atomic parameters have been obtained from a single crystal using the precession method. The structure may be described as composed of units of nearly regular icosahedra in a slightly deformed cubic close packing. This requires the use of three-center or delta bonds, wherein two electrons are …