The vibrations of boron carbide B13C2 have been studied by the valence force model, The 1560-cm(-1) band is ascribed to the antisymetric stretching of the linear chain, and thereby it is IR active only, Large angle-bending forces of the carbon atoms are estimated to agree with the experiment, This conclusion is reasonable, by considering the strong covalent character of the linear chain, At the cost of forming strong covalent bonds in the linear chain, the character of icosahedral bonding is weakened, The decrease in most Raman bands of boron carbides compared with those of alpha-boron can be understood on this basis. (C) 1997 Academic Press. [References: 11]
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