On the theoretical construction of Nb2N2-based superatoms by external field strategies

Design of a Novel Series of Hetero-Binuclear Superhalogen Anions MM′X4− (M = Li, Na; M′ = Be, Mg, Ca; X = Cl, Br)

A series of hetero-binuclear superatom motifs involving chloride/bromide ligands, that is, MM′X₄⁻ (M = Li, Na; M′ = Be, Mg, Ca; X = Cl, Br) anions, have been characterized by using many-body perturbation theory calculations. Large vertical electron detachment energies (VDEs, 5.470–6.799 eV) confirm the superhalogen identity of these anions. A larger VDE value can be obtained by introducing small M or large M′ central atoms and small halogen ligand atoms. Thus, one isomer of LiCaCl₄⁻ possesses the largest VDE value. Besides, when the extra electron is shared by all ligand atoms or three bridging ligand atoms, the isomers have relatively larger VDE values.

External electric field modulated second-order nonlinear optical response and visible transparency in hexalithiobenzene

External electric fields (EEFs) offer a unique opportunity to tune certain activity of molecules by orienting the alignment of the electric field along the specific axis. The second-order NLO response of hexalithiobenzene (C₆Li₆) is very poor due to its first mean hyperpolarizability of 0.5 a.u. Therefore, we have analyzed the effect of EEFs on the structural, electronic properties, and NLO response of C₆Li₆ using a density functional approach. We notice that the structure of the C₆Li₆ molecule remains planar, with the slight change in C-C and C-Li bond lengths, but their stability is increased under the effect of EEFs. By applying EEFs, the conductivity or reactivity of C₆Li₆ is increased as their HOMO-LUMO energy gap is decreased. Furthermore, C₆Li₆ attains a finite dipole moment in the presence of EEF, which increases linearly as the EEF increases. More interestingly, the first static hyperpolarizability of C₆Li₆ is significantly enhanced, becoming as high as 3.4 × 10⁴ a.u. for EEF = 50 × 10^-4 a.u. This suggests the EEF as an effective way to enhance the second-order NLO responses, leading to the design of potential NLO materials. Nevertheless, the visible transparency of C₆Li₆ with and without EEF may suggest its possible applications in optical devices.