Non-centrosymmetric LiBaB₉O₁₅ single crystal: growth and characterization

Abstract

The non-centrosymmetric LiBaB₉O₁₅ single crystal was synthesized by employing high-temperature solution reaction methods at 830 °C. Single-crystal X-ray diffraction analysis showed that it crystallized in the non-centrosymmetric space group R3c, with cell dimensions a = 10.973(1) Å, c = 17.049(2) Å, Z = 6 and V = 1777.8(3) Å³, having 3D frameworks consisting of [B₃O₇]⁵⁻ groups bridged by O atoms, with channels occupied by Li⁺ and Ba²⁺ cations. The atomic positions taken from X-ray diffraction data were optimized by minimizing the forces acting on the atoms. From the relaxed geometry, the electronic structure and the chemical bonding were determined and various spectroscopic features were calculated and compared with experimental data. The state-of-the-art all-electron full-potential linearized augmented plane wave method within the Ceperley–Alder local density approximation and the gradient approximation was used to solve the Kohn–Sham density functional theory equations. Very good agreement between the measurements and the calculations was found. The calculated effective mass ratio of heavy holes $(m_{\text{hh}}^{*} /m_{\text{e}} )$, light holes $(m_{\text{lh}}^{*} /m_{\text{e}} )$ and electrons $(m_{\text{e}}^{*} /m_{\text{e}} )$ was 0.4670, 0.0973 and 0.0120, respectively.