Geometries and energies of small Ge_n (n = 2-6) clusters: An ab initio molecular orbital study

The molecular geometries and relative stabilities of various electronic configurations of Ge_n clusters (n = 2-6) have been investigated by means of ab initio calculations by employing an effective core potential for core electrons and a double zeta plus polarization functions basis set for valence electrons. The calculations have produced the following optimal configurations: Ge₂ (D_∞h, ³∑_g ^-), Ge₃ (equilateral triangle, D_3h ³A′2), Ge₄ (planar rhombus D_2h ¹A_g), Ge₅ (oblate distorted trigonal bipyramid, D_3h ¹A′1), Ge₆ (edge-capped trigonal bipyramid, C_2v ¹A₁). Binding energies have been evaluated by single-point CISD(Q) calculations at the SCF optimal ground-state geometry of the clusters. The results are in qualitative agreement with experimental data. The comparison of Ge_n and Si_n properties shows close similarity between Ge and Si.