A Borosilicide with Clathrate VIII Structure
The high-pressure phase Na8BxSi46-x(3 < x < 5) is the first representative of a borosilicide crystallizing in the rarely occurring clathrate VIII type structure. Crystals with composition Na8B4Si42(space group I43¯ m; a = 9.7187(2) Å Pearson symbol cI54) were obtained at 5-8 GPa and 1200 K. The clathrate I modification exists for the same composition at lower pressure with a larger cell volume (Pm