Elastic properties and electronic structures of lanthanide hexaborides

The structural, elastic, and electronic properties of a series of lanthanide hexaborides (LnB₆) have been investigated by performing ab initio calculations based on the density functional theory using the Vienna ab initio simulation package. The calculated lattice and elastic constants of LnB₆ are in good agreement with the available experimental data and other theoretical results. The polycrystalline Young's modulus, shear modulus, the ratio of bulk to shear modulus B/G, Poisson's ratios, Zener anisotropy factors, as well as the Debye temperature are calculated, and all of the properties display some regularity with increasing atomic number of lanthanide atoms, whereas anomalies are observed for EuB₆ and YbB₆. In addition, detailed electronic structure calculations are carried out to shed light on the peculiar elastic properties of LnB₆. The total density of states demonstrates the existence of a pseudogap and indicates lower structure stability of EuB₆ and YbB₆ compared with others. (paper)