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. 1999