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

• Published in: International journal of quantum chemistry 2023-09, Vol.123 (18), p.n/a
• Main Authors: Feng, Xinxin, Azizi, Alireza, Xu, Tianlv, Yu, Wenjing, Mi, Xiaopeng, Lu, Hui, Früchtl, Herbert, Mourik, Tanja, Kirk, Steven R., Jenkins, Samantha
• Format: Article
• Language: English
• Subjects: Asymmetry; Cartesian coordinates; Chemistry; Critical point; Dimers; Distortion; Eigenvectors; electric field; Lithium; lithium dimer; Mathematical analysis; Metallicity; non‐nuclear attractor; Physical chemistry; Quantum physics; Quantum theory; Rotation; Stretching; Tensors
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/qua.27180

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 (±Ex) and perpendicular (±Ey) to the bond‐path. The ±Ex‐fields and ±Ey‐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 ±Ey‐field and ±Ex‐field was detected in terms of the rotation of the orthogonal triad of stress tensor σ(r) eigenvectors {e1σ, e2σ, e3σ} 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 ±Ey‐fields. Larger movement of the NNAs along the bond‐path correlated with greater bond critical point (BCP) bond metallicity ξ(rb). The effect of applying the ±Ex‐field was compared with unpublished results on neutral Li2 subject to a stretching distortion.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(rb). 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 ±Ex‐field. Suggestions for future work are provided. Top‐upper left: The {pσ (dark‐blue), p′σ (cyan)} stress tensor path‐packets on the neutral Li2 molecular graph for a value of the electric field Ex = +20.0 × 10−4 a.u. The location of the bond critical points (BCPs) and non‐nuclear attractors (NNAs) is denoted by the green and cyan spheres, respectively. Top‐upper right: The corresponding {pσ, p′σ} stress tensor path‐packets for Ex = −20.0 × 10−4 a.u. Top‐lower left: The {pσ, p′σ} stress tensor path‐packets for a value of the electric field Ex = +144.0 × 10−4 a.u. Top‐lower right: The corresponding {pσ, p′σ} stress tensor path‐packets for Ex = −144.0 × 10−4 a.u. The orientation of the Cartesian axes frame x, y, z is kept constant for all molecular graphs. Bottom: The variation of BCP metallicity ξ(rb) with the ±Ex‐field of the neutral Li2 molecular graph, a.u. are used throughout, notice the log10 scale, see Top for further details.