Shi-Xiong Li

This work presents a regulation effect of external electric fields on geometric structures, spectral properties, and reaction activity of (ZnSe) _n (n = 3 and 6) on the basis of density functional theory. The results show that the external electric field has a regulatory effect on all aspects of (ZnSe) _n (n = 3 and 6). The external electric field can change the shape of (ZnSe)₃ from a plane to three-dimensional and stretch (ZnSe) _n (n = 3 and 6) along the direction of the electric field and induce a significant dipole moment transformation (direction and magnitude). This is mainly attributed to the polarization of atoms under the external electric field, which leads to the movement of charges and the movement of charged atoms due to the force. Additionally, the EEF can lower the HOMO–LUMO gap and regulate the UV–vis spectra to form new absorption bands in the visible or near-infrared range, and thus enables (ZnSe) _n (n = 3 and 6) to display color, and is hopeful to regulate the (ZnSe) _n (n = 3 and 6) to present different fluorescence emission wavelengths. Finally, theoretical calculations reveal that the EEF can change the distribution of electrophilic or nucleophilic reaction sites of (ZnSe) _n (n = 3 and 6). In view of the structural deformation and characteristic change of (ZnSe) _n (n = 3 and 6) under the EEF, designing deformable materials driven by EEF is promising, and it is foreseeable that semiconductor clusters with different properties can be designed to be adjusted according to the strength and direction of the applied EEF.

In a recent paper (ChemPhysChem, 2023, 24, e202200947), based on the results computed using DFT method, the perfect core‐shell octahedral configuration Be@B₃₈ and Zn@B₃₈ was reported to be the global minima of the MB₃₈(M=Be and Zn) clusters. However, this paper presents the lower energy structures of MB₃₈(M=Be and Zn) clusters as a quasi‐planar configuration, the Be atom is found to reside on the convex surface of the quasi‐planar B₃₈ isomer, while the Zn atom tends to be attached to the top three B atoms of the quasi‐planar B₃₈ isomer. Our results show that quasi‐planar MB₃₈(M=Be and Zn) at DFT method have lower energy than core‐shell octahedral configuration M@B₃₈(M=Be and Zn). Natural atomic charges, valence electron density, electron localization function (ELF) analyses identify the MB₃₈(M=Be and Zn) to be charge transfer complexes (Be²⁺B₃₈²⁻and Zn¹⁺B₃₈¹⁻) and suggest primarily the electrostatic interactions between doped atom and B₃₈ fragment. The photoelectron spectra of the corresponding anionic structures were simulated, providing theoretical basis for future structural identification.

A new kind of nonmetallic atom-doped boron cluster is described herein theoretically. When a phosphorus atom is added to the B₁₂ motif and loses an electron, a novel B₁₂ cage is obtained, composed of two B₃ rings at both ends and one B₆ ring in the middle, forming a triangular bifrustum. Interestingly, this B₁₂ cage is formed by three B₇ units joined together from three directions at an angle of 120°. When two P atoms are added to the B₁₂ motif, this novel B₁₂ cage is also obtained, and two P atoms are attached to the B₃ rings at both ends of the triangular bifrustum, forming a triangular bipyramid (Johnson solid). Amazingly, the global minimums of neutral, monocationic, and monoanionic P₂B₁₂^+/0/- have the same cage structure with a D_3h symmetry; this is the smallest boron cage with the same structure. The P atom has five valence electrons, according to adaptive natural density partitioning bonding analyses of cage PB₁₂⁺ and P₂B₁₂, in addition to one lone pair, the other three electrons of the P atom combine with an electron of each B atom on the B₃ ring to form three 2c-2e σ bonds and form three electron sharing bonds with B atoms through covalent interactions, stabilizing the B₁₂ cage. The calculated photoelectron spectra can be compared with future experimental values and provide a theoretical basis for the identification and confirmation of P_nB₁₂^- (n = 1-2).

We present a theoretical study of structural evolution, electronic properties, and photoelectron spectra of two sulfur atom-doped boron clusters S₂B_n^0/- (n = 2-13), which reveal that the global minima of the S₂B_n^0/- (n = 2-13) clusters show an evolution from a linear-chain structure to a planar or quasi-planar structure. Some S-doped boron clusters have the skeleton of corresponding pure boron clusters; however, the addition of two sulfur atoms modified and improved some of the pure boron cluster structures. Boron is electron-deficient and boron clusters do not form linear chains. Here, two sulfur atom doping can adjust the pure boron clusters to a linear-chain structure (S₂B₂^0/-, S₂B₃^0/-, and S₂B₄^-), a quasi-linear-chain structure (S₂B₆^-), single- and double-chain structures (S₂B₆ and S₂B₉^-), and double-chain structures (S₂B₅, and S₂B₉). In particular, the smallest linear-chain boron clusters S₂B₂^0/- are shown with an S atom attached to each end of B₂. The S₂B₂ cluster possesses the largest highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap of 5.57 eV and the S₂B₂^- cluster possesses the largest average binding energy E_b of 5.63 eV, which shows the superior chemical stability and relative stability, respectively. Interestingly, two S-atom doping can adjust the quasi-planar pure boron clusters (B₇^-, B₁₀^-, and B₁₂^0/-) to a perfect planar structure. AdNDP bonding analyses reveal that linear S₂B₃ and planar SeB₁₁^- have π aromaticity and σ antiaromaticity; however, S₂B₂, planar S₂B₆, and planar S₂B₇^- clusters have π antiaromaticity and σ aromaticity. Furthermore, AdNDP bonding analyses reveal that planar S₂B₄, S₂B₁₀, and S₂B₁₂ clusters are doubly (π and σ) aromatic, whereas S₂B₅^-, S₂B₈, S₂B₉^-, and S₂B₁₃^- clusters are doubly (π and σ) antiaromatic. The electron localization function (ELF) analysis shows that S₂B_n^0/- (n = 2-13) clusters have different electron delocalization characteristics, and the spin density analysis shows that the open-shell clusters have different characteristics of electron spin distribution. The calculated photoelectron spectra indicate that S₂B_n^- (n = 2-13) have different characteristic peaks that can be compared with future experimental values and provide a theoretical basis for the identification and confirmation of these doped boron clusters. Our work enriches the new database of geometrical structures of doped boron clusters, provides new examples of aromaticity for doped boron clusters, and is promising to offer new ideas for nanomaterials and nanodevices.

A theoretical research of structural evolution, electronic properties, and photoelectron spectra of selenium-doped boron clusters SeB_n^0/− (n = 3–16) is performed using particle swarm optimization (CALYPSO) software in combination with density functional theory calculations. The lowest energy structures of SeB_n^0/− (n = 3–16) clusters tend to form quasi-planar or planar structures. Some selenium-doped boron clusters keep a skeleton of the corresponding pure boron clusters; however, the addition of a Se atom modified and improved some of the pure boron cluster structures. In particular, the Se atoms of SeB₇⁻, SeB₈⁻, SeB₁₀⁻, and SeB₁₂⁻ are connected to the pure quasi-planar B₇⁻, B₈⁻, B₁₀⁻, and B₁₂⁻ clusters, which leads to planar SeB₇⁻, SeB₈⁻, SeB₁₀⁻, and SeB₁₂⁻, respectively. Interestingly, the lowest energy structure of SeB₉⁻ is a three-dimensional mushroom-shaped structure, and the SeB₉⁻ cluster displays the largest HOMO–LUMO gap of 5.08 eV, which shows the superior chemical stability. Adaptive natural density partitioning (AdNDP) bonding analysis reveals that SeB₈ is doubly aromatic, with 6 delocalized π electrons and 6 delocalized σ electrons, whereas SeB₉⁻ is doubly antiaromatic, with 4 delocalized π electrons and 12 delocalized σ electrons. Similarly, quasi-planar SeB₁₂ is doubly aromatic, with 6 delocalized π electrons and 14 delocalized σ electrons. The electron localization function (ELF) analysis shows that SeB_n^0/− (n = 3–16) clusters have different local electron delocalization and whole electron delocalization effects. The simulated photoelectron spectra of SeB_n⁻ (n = 3–16) have different characteristic bands that can identify and confirm SeB_n⁻ (n = 3–16) combined with future experimental photoelectron spectra. Our research enriches the geometrical structures of small doped boron clusters and can offer insight for boron-based nanomaterials.

Here, the ground-state structures, electronic structures, polarizability, and spectral properties of metal-free phthalocyanine (H2Pc) under different external electric fields (EEFs) are investigated. The results show that EEF has an ultrastrong regulation effect on various aspects of H2Pc; the geometric structures, electronic properties, polarizability, and spectral properties are strongly sensitive to the EEF. In particular, an EEF of 0.025 a.u. is an important control point: an EEF of 0.025 a.u. will bend the benzene ring subunits to the positive and negative x directions of the planar molecule. Flipping the EEF from positive (0.025 a.u.) to negative (−0.025 a.u.) flips also the bending direction of benzene ring subunits. The H2Pc shows different dipole moments projecting an opposite direction along the x direction (−84 and 84 Debye for EEFs of −0.025 and 0.025 a.u., respectively) under negative and positive EEF, revealing a significant dipole moment transformation. Furthermore, when the EEF is removed, the molecule can be restored to the planar structure. The transformation of the H2Pc structure can be induced by the EEF, which has potential applications in the molecular devices such as molecular switches or molecular forceps. EEF lowers total energy and reduces highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap; especially, an EEF of 0.025 a.u. can reduce the HOMO–LUMO gap from 2.1 eV (in the absence of EEF) to 0.37 eV, and thus, it can enhance the molecular conductivity. The first hyperpolarizability of H2Pc is 0 in the absence of EEF; remarkably, an EEF of 0.025 a.u. can enhance the first hyperpolarizability up to 15,578 a.u. Therefore, H2Pc under the EEF could be introduced as a promising innovative nonlinear optical (NLO) nanomaterial such as NLO switches. The strong EEF (0.025 a.u.) causes a large number of new absorption peaks in IR and Raman spectra and causes the redshift of electronic absorption spectra. The changes of EEF can be used to regulate the structure transformation and properties of H2Pc, which can promote the application of H2Pc in nanometer fields such as molecular devices.

For a better understanding the effects of nitrogen atom doping on boron clusters, we investigated adopting the ABCluster global search technique and CALYPSO approach combined with density functional theory the lowest energy structures, bonding, electrons delocalization and spectral properties of neutral nitrogen-doped boron clusters, the size of which varies from 10 to 20. The results of its calculations are displayed the global minimum of these clusters are plane or quasi plane structures at n= 11, 13, 15-20, the bowl-like structures at n= 10, 12 and the boat-shaped structure at n=14. It is found that B20N is most stable of all structures. Natural population analysis (NPA) indicates that boron atoms sectional electrons transfer to doped nitrogen atoms. Electron localization Orbital Function (LOL) and Electron Localization Function (ELF) analysis indicate there are strong covalent bonds between doped N atons and B atoms for clusters BnN(n=10-20). In addition, under the same isosurface, the isosurface of B10N is the thickest, indicating that it has the most electrons and the strongest delocalization. Infrared and Raman spectra show that clusters BnN(n=10-20) have a great deal of characteristic peaks, and the strongest IR peaks and Raman peaks are situated at different positions, which can be used to identify the clusters structures and make comparative analysis with future experiments. Electronic absorption spectrum analysis shows that the first absorption peak of these clusters is located in the visible band. The study provides theoretical guidance and basis for the development of novel boron-based nanomaterials.