Influence of an electric field on the topological stability of the neutral lithium dimer

In this investigation, we seek to understand the role of non-nuclear attractors (NNAs) of the neutral Li₂ dimer subjected to an electric (±E) field that is directed parallel (±E_x) and perpendicular (±E_y) to the bond-path. The ±E_x-fields and ±E_y-fields are separately applied to the Li₂ molecular graph until the bond ruptures. The next generation quantum theory of atoms in molecules (NG-QTAIM) interpretation of bonding was constructed with the stress tensor σ(r) eigenvectors on the Hessian of ρ(r) molecular graph. The asymmetry induced by both the ±E_y-field and ±E_x-field was detected in terms of the rotation of the orthogonal triad of stress tensor σ(r) eigenvectors {e_1σ, e_2σ, e_3σ} relative to the Cartesian coordinate frame. The orthogonal triad of Hessian of ρ(r) eigenvectors {e₁, e₂, e₃} however, were only able to detect rotation induced by the high degree of asymmetry present for bent bond-paths induced by the ±E_y-fields. Larger movement of the NNAs along the bond-path correlated with greater bond critical point (BCP) bond metallicity ξ(r_b). The effect of applying the ±E_x-field was compared with unpublished results on neutral Li₂ subject to a stretching distortion. The lack of NNA motion along the bond-path for the stretching distortion correlated with a lower degree of bond metallicity ξ(r_b). The stress tensor σ(r) eigenvectors have a unique ability to detect rotation relative to the Cartesian coordinate frame for high bond-path symmetry occurring for the bond-stretching distortion and application of the ±E_x-field. Suggestions for future work are provided.