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 B^3- 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⁺-B^3--Si⁺ bonding pattern featuring the high anionic state of the boron atom can be identified as a boryl anion.