The high-capacity hydrogen storage abilities of the Ti atoms coated Si@Al12 clusters

The wavefunctions of the HOMO and LUMO of Ti2-Si@Al12 mainly concentrate on the Ti atoms (a). Along with the increase of the adsorbed H2, the contribution of the Ti atoms to the LUMO and HOMO gradually reduce, mirroring the reduction in the activity of the Ti sites caused by the progressive saturation with H2. As to Ti2-Si@Al12·12H2, the Ti atoms contribute none to the LUMO and LUMO as shown in (c), indicating that the two Ti atoms have been saturated. This is in agreement well with the predictions from the 18-electron rule.128