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

Abstract

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 { e 1 , e 2 , e 3 } 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 The effect of applying the ±E x -field was compared with unpublished results on neutral Li2 subject to a stretching distortion.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.