as a result of B12 structural unit, the chemical system of "ideal" boron carbide is frequently written not as B4C, but as B12C3, and the carbon deficiency of boron carbide described when it comes to a mix of the B12C3 https://bookmarksoflife.com/story3708898/the-single-best-strategy-to-use-for-boron-carbide-ceramic-plates