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Optimized geometries of the typical low-lying isomers of neutral BSi n (n = 4-12). The ∆Es are calculated at the CCSD(T)/aug-cc-pVTZ level of theory. Red and yellow balls stand for the B and Si atoms, respectively.
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Size-selected anion photoelectron spectroscopy and theoretical calculations were used to investigate the structural evolution and bonding properties of BSin-/0 (n = 4-12) clusters. The results showed that the B atom in BSi4-12-/0 prefers to occupy the high coordination sites to form more B-Si bonds. The lowest-lying isomers of BSi4-7-/0 primarily a...
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... n (n = 4-12) Neutrals. The geometric structures of BSi n (n = 4-12) neutrals were also optimized at the B3LYP level and displayed in Fig. 4. The most stable isomers of BSi n neutrals are in spin doublet states. We found that the most stable isomers of BSi n (n = 9, 10, and 12) neutrals have dif- ferent geometric structures with their corresponding anions, whereas those of the remaining neutral clusters are similar to their corresponding anions with the bond lengths being ...
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... . This finding is in agreement with the previously theoretical results of BSi 9 . 28 Another possible reason for the high VDE of BSi 9 − is that the neutral structure corresponding to the most stable anionic structure is very high in energy. Indeed, our calculations show that the neutral structure (9D in Fig. 4) similar to 9A is higher in energy than the most stable neutral structure by 0.18 eV, calculated at the CCSD(T) level. This indicates that the excess electron has an obvious effect on the structures of BSi 9 − anion and BSi 9 neutral. In addition, the BSi 9 − cluster implies that the species with a large VDE do not always mean that ...
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Citations
A quantum chemical calculation was performed to investigate the structural and bonding properties of B6C8⁻ anion and B6C8 neutral. The geometries of the most stable isomers of both B6C8⁻ anion and B6C8 neutral were found to be a planar dodecagon with four C2 units separated by four B atoms, which can be further reinforced by the central strong B−B single bond and aromaticity. The bond lengths, Wiberg bond orders, constant charge density surfaces, MOs, and AdNDP analyses were used to give insight into the chemical bonds in the C2h symmetric planar dodecagon of B6C8 neutral. The results showed that the most stable isomer of B6C8 has a closed-shell electronic structure with HOMO–LUMO gap of 2.20 eV and has σ plus π double delocalized bonding characters. More interestingly, the most stable isomer of B6C8 exhibits σ aromaticity and π antiaromaticity.
The evolution of structural and electronic properties, and dynamical fluxionality of B2Gen−/0 (n = 3–12) clusters are investigated using DFT calculations combined with CALYPSO global searching algorithm. The B atoms in B2Gen−/0 incline to bond with each other and more Ge atoms. The theoretical calculations show that B2Ge3−/0 have planar 2D structures, while the geometries of B2Ge4-7−/0 are all exohedral 3D structures dominated by bipyramid-shaped or bowl-shaped based configurations and those of B2Ge8-12−/0 majorly hold prism-shaped based geometries. B2Ge10⁻ and B2Ge10 are confirmed as the threshold sizes of transiting from B2-exohedral to B2-endohedral geometries for anions and neutrals, respectively. Natural population analysis indicates that the electron transfers from Gen skeletons to B atoms. Interestingly, the low-lying isomers of B2Ge4⁻, B2Ge6⁻, B2Ge7−/0, B2Ge8−/0, B2Ge9⁻, and B2Ge12⁻ clusters exhibit dynamical fluxionality. The ΔEI, Δ2E, and ΔEI values versus number of Ge atoms suggest that B2Gen⁻ anions are more stable than B2Gen neutrals, except that B2Ge10 has higher stability than B2Ge10⁻. Molecular orbitals analysis of B2Ge10 indicates that it has σ + π double delocalised bonding patterns and electronic closed-shell configuration with a HOMO–LUMO gap of 2.17 eV. The nucleus-independent chemical shift (NICS) calculations indicate that B2Ge10−/0 clusters have aromaticity.
The structural evolution of medium-sized anionic and neutral Au2Sin (n = 8–20) clusters is investigated by using density functional theory (DFT) calculations and CCSD(T) methods in combination with the particle swarm optimization (CALYPSO) global search algorithm. The geometries of anionic and neutral Au2Sin clusters change from exohedral to endohedral ones with the increasing cluster sizes, and the critical size of forming Au2-endohedral structures for both anionic and neutral clusters is confirmed to be n = 20, in which a C2h symmetric Au2-endohedral cage-like structure is observed. Anionic and neutral Au2Sin clusters are primarily dominated by prism-based geometries with most of them adopting different structural features. It is found that the two Au atoms prefer to occupy low coordination sites and interact with fewer Si atoms. The Au atoms carry negative charges because of the electron-transfer from Sin frameworks. Meanwhile, the two Au atoms have very weak interactions. The second-order energy differences and incremental binding energies of anionic and neutral Au2Sin clusters exhibit an odd–even alternation and Au2Si20−/0 clusters are proven to have the highest chemical stability among these Au–Si clusters. Interestingly, Au2Si8⁻, Au2Si9⁻, Au2Si13⁻, Au2Si15⁻, and Au2Si17⁻ anions, along with Au2Si13, Au2Si14, and Au2Si17 neutrals, have multiplicity of structural forms and their low-lying isomers show dynamical fluxionality due to the low barrier energies.
Silicon clusters doped with transition-metal (TM) atoms not only can hold stable fullerene-like structures, but also can exhibit unique electronic properties. Multiple TM doped silicon clusters are ideal models for investigating semiconductor nanomaterials and localized effects of condensed states. In this work, the geometrical and electronic properties of three V atoms doped anionic, neutral, and cationic Si20 clusters were investigated using quantum chemical calculations and a DFT-based unbiased search based on the particle swarm optimization (CALYPSO) software. The global minima of anionic, neutral, and cationic V3Si20 clusters were found to all hold a fullerene-like silicon cage with 12 Si5 pentagons stabilized by a V3 unit. The three V atoms exhibit strong interactions based on the bonding length, Wiberg bond orders, electronic charge density surfaces, and MOs. Moreover, the V atoms act as the electron acceptors on the basis of the natural population analysis (NPA), atomic dipole moment corrected Hirshfeld (ADCH) population, and atoms in molecules (AIM) population. Furthermore, V3Si20ˉ, V3Si20, and V3Si20+ show significant aromaticity according to the nucleus-independent chemical shift (NICS), aromatic stabilization energy (ASE), and multicenter bond index calculations.
In this work, structural evolution, geometrical and electronic structures of Ta2Sin⁻ and Ta2Sin (n = 3–21) clusters are investigated by joint Crystal structure AnaLYsis by Particle Swarm Optimisation (CALYPSO) global search algorithm and quantum chemical calculations. n = 21 is confirmed as the critical size of forming a Ta2-endohedral silicon cage-like structure for both anionic and neutral Ta2Sin clusters. It is found that the two Ta atoms tend to occupy the high coordination sites and stay close as a whole to bond with the Sin frames, as a result, the global minima of Ta2Sin⁻/0 (n = 3–21) clusters can be all viewed as a central Ta–Ta bonding axis interacted with the surrounding Si atoms. Ta2Sin⁻/0 (n = 3−13) clusters are majorly dominated by the bipyramid or prism-based geometries and Ta2Sin⁻/0 (n = 14−18) clusters are primarily governed by the polyhedral cage-like geometries, whereas Ta2Sin⁻/0 (n = 19−21) clusters are mainly controlled by the prolate geometries. In particular, Ta2Si3⁻ has a D3h symmetric trigonal bipyramid structure, and Ta2Si6⁻ adopts C2h symmetric chair-shaped structure and Ta2Si12⁻ is a C6v symmetric Ta-face-capped hexagonal antiprism with the other Ta atom at the interior of Si12 cage. The odd-even alternations for the relative stabilities of Ta2Sin⁻/0 are observed.
Investigating the structures and properties of large-sized silicon clusters doped with multiple Au atoms can provide valuable microscopic information for gold-catalyzed high-quality Si nanowire and Au−Si alloying reactions, and also for the production of cluster-assembled functional materials. In this work, a quantum chemical investigation on the structural and electronic properties of double Au atoms doped Si20 cluster using density functional theory calculations was performed. The lowest-lying isomers of Au2Si20−/0/+ (The meaning of the acronym: Au2Si20−/0/+ refers to Au2Si20 cluster with a negative charge, neutral state, and a positive charge, respectively.) were found to all adopt a C2h symmetric Au2-endohedral honeycomb-shaped structure consisting of twelve Si5 pentagons. Interestingly, in the anionic, neutral, and cationic Au2Si20, twelve Si5 pentagons can be stabilised by two Au atoms. The two Au atoms in Au2Si20−/0/+ tend to occupy high coordinate sites and exhibit strong aurophilic interactions. In addition, the Au−Si bonds show both covalent and ionic bonding characters. Moreover, Au2Si20−, Au2Si20, and Au2Si20+ are all aromatic.
Unsaturated silicon clusters (siliconoids) are short-lived intermediates during the transition from molecules to the elemental bulk; stable representatives reiterate surface features of silicon materials. The incorporation of suitable heteroatoms into the cluster scaffold of stable siliconoids extends this analogy to the technological process of silicon doping. Here, we report boron- and phosphorus-containing heterosiliconoids with BSi5 and PSi5 core based on the global minimum Si6R6 platform (dubbed benzpolarene for its relationship to benzene). The reductive cleavage of an SiR2 moiety (R = 2,4,6-iPr3C6H2) from Si6R6 selectively yields a dianionic Si5R4²⁻ cluster as its lithium salt. Treatment with Me3SiCl affords the corresponding trimethylsilyl-substituted (Me3Si)2Si5R4. Reaction of Si5R4²⁻ with iPr2NECl2 (E = B, P) yields the unprecedented p- and n-doped heterosiliconoids iPr2NESi5R4. Their peculiar electronic features are compared to those of the hexasilabenzpolarene starting material on grounds of NMR spectroscopy, X-ray diffraction and DFT calculations.
The growth patterns of anionic and neutral B4Sin (n = 4–15) clusters are investigated by using density functional theory (DFT) calculations combined with particle swarm optimization (CALYPSO) software. The geometries of anionic and neutral B4Sin clusters transform from exohedral to endohedral structures with the increasing cluster sizes. B4Si14ˉ anion is the critical size of forming B4-endohedral structure for anionic clusters, while B4Si15 neutral is the threshold size of forming B4-endouhedral structure for neutral clusters. Both anionic and neutral B4Sin (n = 4–15) clusters are primarily dominated by prism-based or bipyramid-based geometries. The global minima of anionic and neutral B4Sin clusters adopt different geometrical structures, except for anionic and neutral B4Si10. The binding energies of B4Sinˉ clusters show an odd-even alternation with the growing number of Si atoms. The B atoms in B4Sinˉ/0 are keen on occupying the high coordination sites to interact with more Si atoms and exhibit B‒B single bonding and B=B double bonding properties. The B atoms are found to carry more negative charges due to charge-transferring from Sin frameworks to B atoms. Interestingly, B4Si4ˉ anion adopts a C2h symmetric bicapped tetragonal bipyramid with σ plus π double bonding characters and has the highest binding energies among the anionic clusters. The bonding interactions in B4Si4ˉ are in the order of B‒B > B‒Si > Si‒Si.
The dynamical fluxionality, multiplicity of geometrical forms, and electronic properties of anionic, neutral, and cationic TanSi12 (n = 1–3) clusters are studied by quantum chemical calculations. The results show that TanSi12−/0/+ (n = 1–3) clusters are dominated by prism-based geometries. Impressively, neutral and cationic TanSi12 (n = 1–3) clusters have multiple geometrical forms and their low-lying isomers exhibit dynamical fluxionality. Ta1Si12− is a D6h symmetric Ta-endohedral Si12 hexagonal prism with highly electronically stability because of satisfying the 18-electrons rule, and having a closing-shell electronic configuration with a large HOMO–LUMO gap of 2.81 eV and delocalised Ta-Si12 ligand interactions. Ta1Si120/+ clusters have a C2v symmetric Ta-endohedral bicapped pentagonal prism. In Ta2Si12−/0/+, a Si5 pentagonal ring and a Si7 heptagonal ring are bridged by the Ta−Ta bonding axis, which is perpendicular to the Si5 and Si7 frameworks. Ta3Si12− adopts a bicapped hexagonal antiprism with one Ta atom encapsulated into the TaSi11 hexagonal antiprism, whereas neutral and cationic Ta3Si12 hold a TaSi5 hexagon and a Si7 heptagon penetrated by the vertical Ta−Ta bond. The Ta atoms in TanSi12−/0/+ (n = 2–3) clusters have strong bonding interactions and the charges are transferred from the Si12 frameworks to the Ta atoms.
