Ab initio molecular orbital calculations on chemical nature of hydrogen on surface of lithium silicate

Chemical nature of superficial hydrogen on the lithium silicate and lithium silicate doped with B, Al and Ga has been investigated by ab initio molecular orbital calculations. The charge distributions and the deprotonation energy have been obtained for the model clusters: LixH4−xSiO4 and LixH7−xSiAO7 (x=0,1; A=B, Al, Ga). It has been shown that the ionicity of surface hydrogen is strengthened by the interaction of dopant units, that operate as an electron acceptor, with surface oxygen, while it is weakened by Li atom bonded to non-bridging oxygen. Also, the deprotonation energy decreases with increasing ionicity of the superficial hydrogen. The H7SiAlO7 cluster models have the largest ionicity of surface hydrogen and the smallest deprotonation energy among the cluster models investigated.