The electronic excitation of Sn associated with the absorption maximum involves multiple evident MO transitions, which makes it not straightforward to explore excitation properties through MO images. In this case, hole-electron analysis can provide more intuitive images and useful information for understanding electron excitation process. The isosurfaces of hole-electron distribution related to critical excitations of the maximum wavelength absorption together with the important parameters, Sr and t indices, for (BN)4C10 are shown in Figure ). Almost all hole and electron isosurfaces are concentrated at C-C units, while the hole and electron distributions on B-N fragment are subtle. This observation is consistent with the case of the main transition orbitals (MTOs) in Figure (b). The Sr index, serving as the overlap function between holes and electrons, is 0.75 a.u., indicating a significant overlap between hole and electron distributions; and the t index, which measures the separation extent between holes and electrons, is -1.06 Å, confirming the low separation.