Crystal structure and chemical bonding of the intermetallic Zintl phase Yb11AlSb9

Abstract

High resolution single crystal synchrotron X-ray diffraction data measured at 15(2) K were used to solve the structure of the complex intermetallic Zintl phase, Yb₁₁AlSb₉ (space group Iba2), made up of Yb cations and polyanions along with isolated Sb anions. The 15(2) K cell parameters are a = 11.7383(4) Å, b = 12.3600(4) Å, c = 16.6796(6) Å. The temperature dependence of the structure was investigated through high resolution synchrotron powder X-ray diffraction (PXRD) data measured from 90 K to 1000 K. Rietveld refinements of the crystal structure revealed near linear thermal expansion of Yb₁₁AlSb₉ with expansion coefficients of 1.49(2) × 10⁻⁵ K⁻¹, 1.71(3) × 10⁻⁵ K⁻¹, 1.13(1) × 10⁻⁵ K⁻¹ for a, b and c, respectively. The chemical bonding in Yb₁₁AlSb₉ was analyzed using atomic Hirshfeld surfaces, and the analysis supports the presence of the structural elements of Yb cations, [AlSb₄]⁹⁻ tetrahedra, [Sb₂]⁴⁻ dimers and isolated Sb³⁻ anions. However, indications of interatomic interactions between the Zintl anions and the Yb cations were also observed.