(HBNH)n团簇的结构和稳定性

Structures and thermodynamic properties of the imidoboranes （HBNH）n （n=1-16） have been investigated theoretically at the B3LYP/6-31G^＊ level of theory. Needle-shaped oligomers that violate the isolated square rule were found to be more stable than cage isomers. The needle-shaped oligomer with n=16 was predicted to be exceptionally stable at low temperature, hexamer and octamer clusters dominated the gas phase at higher temperature. The highest oligomerization degree of the spontaneous cluster fomation has been estimated. It was concluded that generation of the gas phase （HBNH）n clusters with oligomerization degree n ≥24 was viable, making these species possible intermediates involved in the gas phase generation of BN nanoparticles.     

Making and breaking of small water clusters: A combined quantum chemical and molecular dynamics approach

We present a combined quantum chemical and molecular dynamics study of cyclic and noncyclic water n-mers ([(H₂O]_n, n = 2–6) at four different temperatures and showcase that the dynamics of small water clusters can reproduce the known properties of bulk water reasonably well. We investigate the making and breaking of the water clusters by computing the hydrogen bond strengths, average lifetimes, and relative stabilities, which are important to understand the complex solution dynamics. We compare the behavior of water clusters in the gas phase and in the solution phase as well as the variation in the properties as a function of cluster size and highlight the notably more interesting cluster dynamics of the water trimer when compared to the other water clusters. © 2019 Wiley Periodicals, Inc.     

Density Functional Theory Study on (Cl2GaN3)n(n=1–4) Clusters

The molecular geometries, vibrational properties, and thermodynamic properties of the clusters (Cl₂GaN₃)_n(n=1–4) have been predicted at the B3LYP/6‐311+G* level. The optimized clusters (Cl₂GaN₃)_n (n=2–4) all possess cyclic structures containing Ga N_α Ga linkages. The relationships between geometrical parameters and oligomerization degree n are discussed. The gas‐phase structures of the trimers prefer to exist in boat‐twisting conformation. As for the tetramer, the S₄ symmetry structure is the most stable. The infrared spectra are obtained and assigned by vibrational analysis. Thermodynamic properties derived from the infrared spectra on the basis of statistical thermodynamic principles are linearly correlated with the oligomerization degree n as well as the temperature. Meanwhile, thermodynamic analysis of the gas‐phase reaction suggests that the oligomerization is exothermic and favorable under high temperature.     

Density functional theory study on (F2AlN3) n (n = 1–4) clusters

Possible geometrical structures and relative stabilities of (F₂AlN₃) _n (n = 1–4) clusters were studied using density functional theory at the B3LYP/6-311+G* level. The optimized clusters (F₂AlN₃) _n (n = 2–4) possess cyclic structure containing Al–N_α–Al linkages, and azido in azides has linear structure. The IR spectra of the optimized (F₂AlN₃) _n (n = 1–4) clusters have three vibrational sections, the whole strongest vibrational peaks lie in 2218–2246 cm⁻¹, and the vibrational modes are N₃ asymmetric stretching vibrations. Trends in thermodynamic properties with temperature and oligomerization degree n are discussed, respectively. A study of their thermodynamic properties suggests that monomer 1A forms the most stable clusters (2A, 3A, and 4B) can occur spontaneously in the gas phase at temperatures up to 800 K.     

Structural and electronic properties of stable Aun (n = 2–13) clusters: A density functional study

All-electron scalar relativistic calculations have been performed to investigate the electronic structures of neutral gold clusters (Au_n, n = 2–13) in the gas phase using density functional theory with the generalized gradient approximation. Full geometry optimizations of topologically different clusters and clusters belonging to different symmetry groups have been carried out. Binding energies, ionization potentials, electron affinities, and chemical hardness values are calculated and they are found to be comparable with the available experimental and theoretical results. The most stable structure of each of the cluster has a two-dimensional planar configuration. A three dimensional distorted Y shaped structure (4b) for Au₄, a tri-capped triangle (6b), a chair (6f), and a see-saw structure (6j) for Au₆, an eclipsed sandwich structure (7g) for Au₇, a condensed trigonal bipyramid (9e) and a boat shaped structure (9f) for Au₉, a staggered sandwich (11c) and an eclipsed sandwich structure (11d) for Au₁₁, a ladderane structure (12d) for Au₁₂, and a staggered (13d) and a distorted sandwich structure (13e) for Au₁₃ are characterized for the first time in this work.     

Bare Clusters Derived from Protein Templates: Au25+, Au38+ and Au102+

A discrete sequence of bare gold clusters of well‐defined nuclearity, namely Au₂₅⁺, Au₃₈⁺ and Au₁₀₂⁺, formed in a process that starts from gold‐bound adducts of the protein lysozyme, were detected in the gas phase. It is proposed that subsequent to laser desorption ionization, gold clusters form in the gas phase, with the protein serving as a confining growth environment that provides an effective reservoir for dissipation of the cluster aggregation and stabilization energy. First‐principles calculations reveal that the growing gold clusters can be electronically stabilized in the protein environment, achieving electronic closed‐shell structures as a result of bonding interactions with the protein. Calculations for a cluster with 38 gold atoms reveal that gold interaction with the protein results in breaking of the disulfide bonds of the cystine units, and that the binding of the cysteine residues to the cluster depletes the number of delocalized electrons in the cluster, resulting in opening of a super‐atom electronic gap. This shell‐closure stabilization mechanism confers enhanced stability to the gold clusters. Once formed as stable magic number aggregates in the protein growth medium, the gold clusters become detached from the protein template and are observed as bare Au_n⁺ (n=25, 38, and 102) clusters.     

Decomposition of Copper Formate Clusters: Insight into Elementary Steps of Calcination and Carbon Dioxide Activation

The decomposition of copper formate clusters is investigated in the gas phase by infrared multiple photon dissociation of Cu(II)_n(HCO₂)_2n+1⁻, n≤8. In combination with quantum chemical calculations and reactivity measurements using oxygen, elementary steps of the decomposition of copper formate are characterized, which play a key role during calcination as well as for the function of copper hydride based catalysts. The decomposition of larger clusters (n > 2) takes place exclusively by the sequential loss of neutral copper formate units Cu(II)(HCO₂)₂ or Cu(II)₂(HCO₂)₄, leading to clusters with n=1 or n=2. Only for these small clusters, redox reactions are observed as discussed in detail previously, including the formation of formic acid or loss of hydrogen atoms, leading to a variety of Cu(I) complexes. The stoichiometric monovalent copper formate clusters Cu(I)_m(HCO₂)_m+1⁻, (m=1,2) decompose exclusively by decarboxylation, leading towards copper hydrides in oxidation state +I. Copper oxide centers are obtained via reactions of molecular oxygen with copper hydride centers, species containing carbon dioxide radical anions as ligands or a Cu(0) center. However, stoichiometric copper(I) and copper(II) formate Cu(I)(HCO₂)₂⁻ and Cu(II)(HCO₂)₃⁻, respectively, is unreactive towards oxygen.     

Vibrational spectra and structural features of noble gas fluorides in cryogenic and nonaqueous solutions

Data on the vibrational spectra of noble gas fluorides in the gas phase and in cryogenic and nonaqueous solutions are considered in detail. Based on analysis of the IR spectra of xenon fluorides dissolved in liquid Kr and Xe, it is concluded that the XeF₆ molecule possesses the geometry of a distorted octahedron withC _3v symmetry. The contours of spectral lines of totally symmetric stretching modes in the Raman spectra of noble gas fluorides in nonaqueous solutions are considered; the mechanisms of formation contours of these lines, the dynamic parameters of XeF _n (n=2, 4, 6) and KrF₂, and the characteristic times of intramolecular rearrangements in the nonrigid XeF₆ molecule are analyzed. It is concluded that in the XeF₂-HF and XeF₆-HF systems, a number of associates and ionic clusters are formed due to the donor-acceptor interaction of the Lewis bases and acids. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 560–582, April, 1998.     

Size effect on the structural and electronic properties of lead telluride clusters

Theoretical computations of (PbTe)_n (n = 21–45) clusters based on density functional theory have demonstrated that at cluster size of (PbTe)₂₂ there is a transition from the strong preference of fivefold coordination to sixfold coordination of lead and tellurium atoms. (PbTe)₂₄ cluster is the smallest tetragonal structure in which its central atoms have bulk‐like coordination. This quantum dot (QD) contains a single‐unit cell of lead telluride crystal, thus can be considered as an “infant crystal.” (PbTe)₃₂ cluster is a perfectly cubic cluster for which its inner (PbTe)₄ core enjoys bulk‐like coordination. This (PbTe)₄ core unit of (PbTe)₃₂ cubic cluster has exactly the same environment as a primitive cell of lead telluride crystal. The (PbTe)_8n, (n ≥ 3) clusters are the magic number species with bulk‐like structure such that (n = 3–5) the nanoblocks considered here (PbTe)₂₄, (PbTe)₃₂, and (PbTe)₄₀ clusters exhibiting bulk‐like structure that can be replicated to obtain the bulk crystal. The calculated dimensions of this special clusters provided a rubric for understanding the pattern of aggregation, that is, the creation of defined nanoblocks [(PbTe)_8n, (n ≥ 6)], when they were accumulated on an appropriate surface. It is evident that the QDs (PbTe)_8n, (n = 3–5) clusters show high stability compared to their neighboring clusters. This can also be seen from the second‐order energy difference, binding, and fragmentation energy graphs. © 2014 Wiley Periodicals, Inc.     

Optimization of bimetallic Cu–Au and Ag–Au clusters by using a modified adaptive immune optimization algorithm

A modified adaptive immune optimization algorithm (AIOA) is designed for optimization of Cu–Au and Ag–Au bimetallic clusters with Gupta potential. Compared with homoatom clusters, there are homotopic isomers in bimetallic cluster, so atom exchange operation is presented in the modified AIOA. The efficiency of the algorithm is tested by optimization of Cu_nAu_38‐n (0 ≤ n ≤ 38). Results show that all the structures with the putative global minimal energies are successfully located. In the optimization of Ag_nAu_55‐n (0 ≤ n ≤ 55) bimetallic clusters, all the structures with the reported minimal energies are obtained, and 36 structures with even lower potential energies are found. On the other hand, with the optimized structures of Cu_nAu_55‐n, it is shown that all 55‐atom Cu–Au bimetallic clusters are Mackay icosahedra except for Au₅₅, which is a face‐centered cubic (fcc)‐like structure; Cu₅₅, Cu₁₂Au₄₃, and Cu₁Au₅₄ have two‐shell Mackay icosahedral geometries with I_h point group symmetry. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009     

激光溅射金属等离子体与醇类分子束反应的研究：产物离子对分子束状态的依赖性

The gas phase reactions of metal plasma with alcohol clusters were studied by time of flight mass spectrometry （TOFMS） using laser ablation-molecular beam （LAMB） method. The significant dependence of the product cluster ions on the molecular beam conditions was observed. When the plasma acted on the low density parts of the pulsed molecular beam, the metal-alcohol complexes M^＋An （M=Cu, Al, Mg, Ni and A=C2H5OH, CH3OH） were the dominant products, and the sizes of product ion clusters were smaller. While the plasma acted on the high density part of the beam, however, the main products turned to be protonated alcohol clusters H^＋An and, as the reactions of plasma with methanol were concerned, the protonated water-methanol complexes H3O^＋（CH3OH）n with a larger size （n≤12 for ethanol and n≤24 for methanol）. Similarly, as the pressure of the carrier helium gas was varied from 1 × 10^5 to 5 × 10^5 Pa, the main products were changed from M^＋An to H^＋An and the sizes of the clusters also increased. The changes in the product clusters were attributed to the different formation mechanism of the output ions, that is, the M^＋An ions came from the reaction of metal ion with alcohol clusters, while H^＋An mainly from collisional reaction of electron with alcohol clusters.     

Electron impact ionization of silver clusters Ag n,n≦36

Electron impact ionization of gas phase silver clusters Ag _n ,n≦36 has been achieved in the threshold region. The vertical ionization potentials in this region clearly demonstrate the evidence of shell effects as well as a distinct even-odd oscillation up ton?20. Their general size dependence is somewhat different from that of the alkali metal clusters due to the presence of thed-electrons.     

Clustering of sulfamic acid: ESI MS and theoretical study

Sulfamic acid has wide application in industry and has been suggested to act as an effective nucleation agent for the formation of aerosols and cloud particles. From the point of view of the role that sulfamic acid may play in aerosol formation, the study of its homoaggregation is important. Gas phase clustering study was performed for sulfamic acid H₃N·SO₃, (ASA), from water and methanol–water solutions, by help of a TOF‐Q spectrometer equipped with electrospray ionization source, in the negative‐ion mode. The structure and stability of the (H₃N·SO₃)_n and [(H₃N·SO₃)_n‐H]^? (n = 1–6) were studied using DFT/B3LYP/aug‐cc‐pVDZ method. The ESI MS study evidenced that both singly and doubly charged clusters are formed when the acids are electrosprayed from water solutions; they may be described as [(H₃N·SO₃)_n‐zH]^z? where z = 1 or 2. The largest identified clusters are built of 20 monomers. The theoretical studies showed that formation of higher order (ASA)_n aggregates in the gas phase is energetically profitable. In contrast with the gas phase, aqueous solution does not favor the formation of (ASA)_n aggregates. The study led to the conclusion that the ASA clusters are formed in the gas phase under the experimental conditions of the mass spectrometer. A hypothetical mechanism concerning the formation of the doubly negatively charged anionic aggregates is discussed. The obtained data suggest that small (NH₃·SO₃)_n aggregates may also contribute to formation of aerosols in heavily polluted atmospheres with relatively large NH₃ concentration. Copyright © 2015 John Wiley & Sons, Ltd.     

INORGANIC RINGS AND CLUSTERS AS SINGLE-SOURCE PRECURSORS TOWARD STOICHIOMETRY CONTROLLED SYNTHESIS OF MATERIALS: GAS PHASE CHEMISTRY IN COMMAND

Potential of the inorganic rings and clusters as single-source precursors to 13–15 binary materials and composites is examined employing quantum-chemical methods. Importance of the gas phase association reactions during MOCVD processes from organometallic and hydride precursors is emphasized. Generation of the gas phase [HMYH]_n clusters (M = Al,Ga,In; Y = N,P,As) with large oligomerization degree (n ≥ 30) is thermodynamically favorable even at high temperature conditions (1000 K) for all M,Y pairs. High stability of the N-containing clusters makes mixed metal oligomer imidometallanes excellent single-source precursors for the stoichiometry-controlled MOCVD of 13–15 composites.     

Theoretical investigation of gas phase ethanol–(water)n (n = 1–5) clusters and comparison with gas phase pure water clusters (water)n (n = 2–6)

Various properties (such as optimal structures, structural parameters, hydrogen bonds, natural bond orbital charge distributions, binding energies, electron densities at hydrogen bond critical points, cooperative effects, and so on) of gas phase ethanol–(water)_n (n = 1–5) clusters with the change in the number of water molecules have been systematically explored at the MP2/aug‐cc‐pVTZ//MP2/6‐311++G(d,p) computational level. The study of optimal structures shows that the most stable ethanol‐water heterodimer is the one where exists one primary hydrogen bond (O? H…O) and one secondary hydrogen bond (C? H …O) simultaneously. The cyclic geometric pattern formed by the primary hydrogen bonds, where all the molecules are proton acceptor and proton donor simultaneously, is the most stable configuration for ethanol–(water)_n (n = 2–4) clusters, and a transition from two‐dimensional cyclic to three‐dimensional structures occurs at n = 5. At the same time, the cluster stability seems to correlate with the number of primary hydrogen bonds, because the secondary hydrogen bond was extremely weaker than the primary hydrogen bond. Furthermore, the comparison of cooperative effects between ethanol–water clusters and gas phase pure water clusters has been analyzed from two aspects. First of all, for the cyclic structure, the cooperative effect in the former is slightly stronger than that of the latter with the increasing of water molecules. Second, for the ethanol–(water)₅ and (water)₆ structure, the cooperative effect in the former is also correspondingly stronger than that of the latter except for the ethanol–(water)₅ book structure. © 2012 Wiley Periodicals, Inc.     

Stretching vibrations and structure of (HF) n (n=4–8) clusters

IR spectra of 24 structural isomers of (HF) _n (n=4–8) clusters were calculated in the framework of semiempirical theory of polyatomic molecule vibrations. Based on the results obtained and available experimental data it is proposed that (HF) _n associates comprising 3–5-membered cycles with attached monomeric HF units are present in molecular beams and gas phase.Ab initio calculations performed by the SCF method show the existence of local minima corresponding to such structures on the potential energy surface of (HF) _n clusters (n=4–6). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 435–443, March, 1997.     

Tautomerism and proton transfer in photoionized acetaldehyde and acetaldehyde–water clusters

Understanding the gas‐phase chemistry of acetaldehyde can be challenging because the molecule can assume several tautomeric forms, namely keto, enol and carbene. The two last forms are the most stable ionic forms. Here, insight into the gas‐phase cluster ion chemistry of homogeneous acetaldehyde and mixed water–acetaldehyde clusters is provided by mass spectrometry/vacuum ultraviolet photoionization combined with density functional theory calculations. (AA)_nH⁺ clusters (AA = acetaldehyde) and mixed (AA)_nH₃O⁺ clusters were detected using tunable vacuum ultraviolet photoionization. Barrierless proton transfers were observed during the geometry optimization of the most stable dimer structures and helped to explain the cluster ion chemistry induced by photoionization, namely the formation of deprotonated tautomers and protonated keto tautomers. Water was found to catalyze the keto–enol and keto–carbene isomerizations and facilitate the proton transfer from the ionized enol or carbene part of the cluster to the neutral keto part, resulting in protonated keto structures. The production of protonated keto structures was identified to be the main fragmentation channel following ionization of the homogeneous acetaldehyde cluster and a channel for ionized mixed clusters as well. These findings are significant for a broad range of fields, including current atmospheric models, because acetaldehyde is one of the most prominent organic species in the troposphere and ions play a crucial role in aerosol formation. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Electrochemistry of Alkylidynetrihydridotriruthenium Clusters with Apical π-Substituents

The clusters, (-H)₃Ru₃( ₃-CY)(CO)_9–n (PPh₃) _n [Y=–CH₂CHCH₂, n=0 (1); Y=–CH₂CHCH₂, n=3 (2); Y=–C₆H₄CH₃, n=0 (3); Y=–C₆H₄CH₃, n=3 (4)], have been synthesized in good yields and characterized by IR and NMR spectroscopy and by elemental analysis. The electrochemical properties of these clusters is also reported. These data indicate that the -system of the apical substituent does not interact significantly with the cluster and should be available for further chemistry.     

Recent Advances in Aromatic Antimony Clusters

This paper highlights the compounds containing Sb cluster fragments, either synthesized in the solid‐state, discovered from the gas phase, or only theoretically predicted. These Sb_n clusters feature unique chemical bonding, fascinating structures, and special stabilities that can be well rationalized by aromaticity or antiaromaticity. A deep understanding to their electronic structures is essential and will greatly facilitate the experimental synthesis of new Sb_n cluster‐based materials.     

Stability,Infrared Spectra and Electronic Structures of (ZrO2)n(n=3-6)Clusters:DFT Study

The stability, infrared spectra and electronic structures of (ZrO₂)_n (n=3–6) clusters have been investigated by using density‐functional theory (DFT) at B3LYP/6‐31G* level. The lowest‐energy structures have been recognized by considering a number of structural isomers for each cluster size. It is found that the lowest‐energy (ZrO₂)₅ cluster is the most stable among the (ZrO₂)_n (n=3–6) clusters. The vibration spectra of Zr? O stretching motion from terminal oxygen atom locate between 900 and 1000 cm^?1, and the vibrational band of Zr? O? Zr? O four member ring is obtained at 600–700 cm^?1, which are in good agreement with the experimental results. Mulliken populations and NBO charges of (ZrO₂)_n clusters indicate that the charge transfers occur between 4d orbital of Zr atoms and 2p orbital of O atoms. HOMO‐LUMO gaps illustrate that chemical stabilities of the lowest‐energy (ZrO₂)_n (n=3–6) clusters display an even‐odd alternating pattern with increasing cluster size.