Table 1: Some geometrical parameters (Å and degrees), the averaged net atomic charge, aenergy level of HOMO and LUMO, and the HOMO-LUMO energy gap (hartree)c of Ti-T8 and Si-T8 at the B3LYP/6-311+G(d) level.

AA-O A-H <AOA <OAO Cb-A Ca-O

Si1.6441.460148.4109.22.7442.690
Ti1.8111.697149.1109.13.0232.951

A HOMOcLUMOc

Si2.131 (0.767)−1.268 (−0.474)−0.319 [−0.483]−0.007 [0.052]0.312 [0.535]
Ti1.313 (0.202)−0.787 (−0.110)−0.328 [−0.464]−0.139 [0.019]0.189 [0.483]

aNBO and Mulliken (in parentheses) net atomic charges on A (Si and Ti) and O atoms.
bC is the center of the cage.
cThe HF/6-311+G(d) values are in square brackets.