First principles gas phase study of the structures, energetics and spectroscopic parameters of aluminium antimonide, Al _x Sb _y (x + y = 3, 5), clusters

Abstract

Theoretical methods (DFT/B3LYP and MP2) have been used to optimize the geometries of the Al _x Sb _y (x + y = 3, 5) clusters and their anions. Single point energy computations at CCSD(T) level have also been performed using the optimized B3LYP and MP2 structures. The basis sets used for Al and Sb atoms are 6-311+G(2d) and LANL2DZdp ECP, respectively. Harmonic vibrational frequency computations were carried out to confirm the nature of the stationary points. We report the structural and spectroscopic parameters of the named clusters. We also report the relative energy of the clusters, the vertical electron detachment energy, the adiabatic electron detachment energy and the adiabatic electron affinity. The most stable structures at the CCSD(T)//MP2 level are, the D _∞h linear structure (AlSb₂) and the C _2v V-bent structure (AlSb ⁻₂ ), the C _2v V-bent structure (Al₂Sb and its anion), the C _2v edge-capped tetrahedron (Al₂Sb₃ and its anion), the C _2v trigonal bipyramidal structure (Al₃Sb₂ and its anion), the C _4v square pyramidal (AlSb₄) and a C _2v ground structure for its anion, the C _2v planar trapezoidal structure (Al₄Sb) and the C _2v edge-capped tetrahedron (Al₄Sb⁻). The adiabatic electron affinities calculated at the CCSD(T)//MP2 level are 2.17 eV (AlSb₂), 2.17 eV (Al₂Sb), 2.38 eV (Al₂Sb₃), 2.76 eV (Al₃Sb₂), 2.21 eV (AlSb₄) and 2.03 eV (Al₄Sb). The findings of this research are analysed, discussed and compared with the analogous picnogenides clusters.