Molecular orbital calculations of chemical bonding states of solute elements in amorphous silicon nitride ceramics

We performed ab initio Hartree-Fock molecular orbital calculations of solute elements in amorphous silicon nitride (Si-N) ceramics. To investigate effects of solute elements, X, such as boron, carbon, aluminum, silicon, and phosphorus, on stabilization of the Si-N network, we used model clusters representing local atomic structures in the SiN network, and the solute elements were substituted for nitrogen. Bonding characteristics around the solute elements were analyzed, and bond energies of SiX were also calculated using model clusters. It was found that, among these solute elements in amorphous Si-N, the Si-C bond is able to make the Si-N network more stable due to its high covalency.