The dynamic effective charges of icosahedral boron by the bond-charge model

The polar vibrations of icosahedral boron molecules B-12 have been studied by the adiabatic bond-charge model, assuming that the bond charges are located at the centers of the triangular surfaces. It is shown that the distribution of the can be greatly deformed without much cost of energy. As a consequence, a large effective charge can be obtained, in contrast to the prediction by the shell model. This result is in agreement with an experiment of IR absorption intensity.