Atomic structure and vibrational properties of icosahedral B4C boron carbide

The atomic structure of icosahedral B4C boron carbide is determined by comparing existing infrared absorption and Raman diffusion measurements with the predictions of accurate ab initio lattice dynamical calculations performed for different structural models, a task presently beyond x-ray and neutron diffraction ability. By examining the inter- and intraicosahedral contributions to the stiffness we show that. contrary to recent conjectures, intraicosahedral bonds are harder.