New synthesized highly anisotropic Ba pentaborate crystals

Abstract

Giant anisotropy in the charge density distribution for different crystal sequences of the new synthesized pentaborate Ba[B 5O 8(OH) 3] crystals was predicted on the basis of self-consistent band structure calculations. Self-consistent calculations using a norm-conserving nonlocal pseudopotential showed that the anisotropy observed results from the specific geometry of clusters under consideration, as well as from the anisotropy of covalent 2pO2pB bonds within the layers and weaker 2pO2pO bonds between the layers. A comparison of the calculated imaginary part of dielectric susceptibility with ellipsometric measurements was made in order to verify our calculations. The role played by Ba cations in the formation of the observed anisotropy was proved. A correlation between the band structure dispersion and electron charge density distribution is shown.