Strong Effect of Anionic Boron-Induced Bonding in LiBSi2.

Results of periodic DFT simulations have been used to gain a new view of the crystal chemistry of LiBSi2 in terms of computational modeling of the LiB + 2Si → LiBSi2 synthesis reaction. It was shown that both the strong alkali-metal-[BSi2]- interaction and the rich behavior of B-Si couplings are the main distinctive features of the chemical bonding picture in LiBSi2. In particular, an interplay between charge transfer from easily ionizable lithium linear chains to the boron atoms and strong covalent connectivities in the tetrahedral B-Si framework is of great importance for the bonding architecture in LiBSi2. The activation of positively ionized silicon species Si+ and the formation of electron-rich B3- anions in the [BSi2]- group were found to play a key role in providing the stability of boron-silicon polar covalent bonds. It was suggested that the Si+-B3--Si+ bonding pattern featuring the high anionic state of the boron atom can be identified as a boryl anion.