Interaction of diatomic germanium with lithium atoms: Electronic structure and stability Available to Purchase

Quantum chemical calculations were applied to investigate the electronic structure of mono-, di-, and trilithiated digermanium $(Ge2Lin)$ and their cations $(n=0–3)$⁠. Computations using a multiconfigurational quasidegenerate perturbation approach based on complete active space self-consistent-field wave functions, and density functional theory reveal that $Ge2Li$ has a $B12$ ground state with a doublet-quartet energy gap of $33kcal∕mol$⁠. $Ge2Li2$ has a singlet ground state with a $Au3-A11$ gap of $29kcal∕mol$⁠, and $Ge2Li3$ a doublet ground state with a $B24-A22$ separation of $22kcal∕mol$⁠. The cation $Ge2Li+$ has a $B13$ ground state, being $13kcal∕mol$ below the open-shell $B11$ state. The computed electron affinities for diatomic germanium are $EA(1)=1.9eV$⁠, $EA(2)=−2.5eV$⁠, and $EA(3)=−6.0eV$⁠, for $Ge2−$⁠, $Ge22−$⁠, and $Ge23−$⁠, respectively, indicating that only the monoanion is stable with respect to electron detachment, in such a way that $Ge2Li$ is composed by $Ge2−∙Li+$ ions. An “atoms-in-molecules” analysis shows the absence of a ring critical point in $Ge2Li$⁠. An electron localization function analysis on $Ge2Li$ supports the view that the Ge–Li bond is predominantly ionic; however, a small covalent character could be anticipated from the analysis of the Laplacian at the Ge–Li bond critical point. The ionic picture of the Ge–Li bond is further supported by a natural-bond-order analysis and the Laplacian of the electron density. The calculated Li affinity value for $Ge2$ is $2.08eV$⁠, while the $Li+$ cation affinity value for $Ge2−$ is $5.7eV$⁠. The larger $Li+$ cation affinity value of $Ge2−$ suggests a $Ge2−Li+$ interaction and thus supports the ionic nature of Ge–Li bond. In $GeLi4$ and $Ge2Li$⁠, the presence of trisynaptic basins indicates a three-center bond connecting the germanium and lithium atoms.