1,2,3-三氮杂苯－(水)3复合物多体相互作用

The interaction between 1,2,3-triazine and three water molecules was studied using density functional theory B3LYP method at 6-31-t＋＋G^＊＊ basis set. Various structures for 1,2,3-triazine-（water）n （n= 1, 2, 3） complex were investigated and the different lower energy structures were reported. Many-body analysis was also carded out to obtain relaxation energy and many-body interaction energy （two, three, and four-body）, and the most stable conformer has the basis set superposition error corrected interaction energy of -- 102.61 kJ/mol. The relaxation energy, two- and three-body interactions have significant contribution to the total interaction energy whereas four-body interaction was very small for 1,2,3-triazine-（water）3 complex.     

Hydrogen bonding interaction between 1,4‐dioxane and water

This work reports an interaction of 1,4‐dioxane with one, two, and three water molecules using the density functional theory method at B3LYP/6‐311++G* level. Different conformers were studied and the most stable conformer of 1,4‐dioxane‐(water)_n (n = 1–3) complex has total energies ?384.1964038, ?460.6570694, and ?537.1032381 hartrees with one, two, and three water molecules, respectively. Corresponding binding energy (BE) for these three most stable structures is 6.23, 16.73, and 18.11 kcal/mol. The hydrogen bonding results in red shift in O? O stretching and C? C stretching modes of 1,4‐dioxane for the most stable conformer of 1,4‐dioxane with one, two, and three water molecules whereas there was a blue shift in C? O symmetric stretching and C? O asymmetric stretching modes of 1,4‐dioxane. The hydrogen bonding results in large red shift in bending mode of water and large blue shift in symmetric stretching and asymmetric stretching mode of water. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Theoretical prediction for the structures of gas phase lithium oxide clusters: (Li2O)n (n = 1–8)

We apply genetic algorithm combining directly with density functional method to search the potential energy surface of lithium‐oxide clusters (Li₂O)_n up to n = 8. In (Li₂O)_n (n = 1–8) clusters, the planar structures are found to be global minimum up to n = 2, and the global minimum structures are all three‐dimensional at n ≥ 3. At n ≥ 4, the tetrahedral unit (TU) is found in most of the stable structures. In the TU, the central Li is bonded with four O atoms in sp³ interactions, which leads to unusual charge transformation, and the probability of the central Li participating in the bonding is higher by adaptive natural density partitioning analysis, so the central Li is in particularly low positive charge. At large cluster size, distortion of structures is viewed, which breaks the symmetry and may make energy higher. The global minimum structures of (Li₂O)₂, (Li₂O)₆, and (Li₂O)₇ clusters are the most stable magic numbers, where the first one is planar and the later both have stable structural units of tetrahedral and C_4v. © 2012 Wiley Periodicals, Inc.     

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.     

Density functional theory study of geometry and stability of small Zrn (n = 2–10) clusters

Geometric structures, electronic properties, and stabilities of small Zr_n and Zr (n = 2–10) clusters have been investigated using density functional theory with effective core potential LanL2DZ basis set. For both neutral and charged systems, several isomers and different multiplicities were studied to determine the lowest energy structures. Many most stable states with high symmetry were found for small Zr_n clusters. The most stable structures and symmetries of Zr clusters are the same as the neutral ones except n = 4 and 7. We found that the clusters with n > 3 possess highly compact structures. The clusters are inclined to form the caged‐liked geometry containing pentagonal structures for n > 8, which is in favor of energy. From the formation energy and second‐order energy difference, we obtained that 2‐, 5‐, 7‐atoms of neutral and 4‐, 7‐atoms cationic clusters are the magic numbers. Furthermore, the highest occupied molecular orbital‐lowest unoccupied molecular orbital gaps display that the Zr₃, Zr₆, Zr, and Zr are more stable in chemical stability. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Electrocatalytic Production of C3‐C4 Compounds by Conversion of CO2 on a Chloride‐Induced Bi‐Phasic Cu2O‐Cu Catalyst

Electrocatalytic conversion of carbon dioxide (CO₂) has recently received considerable attention as one of the most feasible CO₂ utilization techniques. In particular, copper and copper‐derived catalysts have exhibited the ability to produce a number of organic molecules from CO₂. Herein, we report a chloride (Cl)‐induced bi‐phasic cuprous oxide (Cu₂O) and metallic copper (Cu) electrode (Cu₂O_Cl) as an efficient catalyst for the formation of high‐carbon organic molecules by CO₂ conversion, and identify the origin of electroselectivity toward the formation of high‐carbon organic compounds. The Cu₂O_Cl electrocatalyst results in the preferential formation of multi‐carbon fuels, including n‐propanol and n‐butane C3–C4 compounds. We propose that the remarkable electrocatalytic conversion behavior is due to the favorable affinity between the reaction intermediates and the catalytic surface.     

Ab initio study of n-tetrasilane cation and anion radicals as models of doped linear polysilanes

The geometric and electronic structures of n-tetrasilane cation and anion radicals as models of doped linear polysilanes are studied theoretically using an ab initio molecular orbital method at the UMP2/6–31 + G(d, p) level of calculations. It is found that the trans-conformations in these molecules are the most stable structures in each ground state and that the energy differences between the cis- and trans-conformations are 3 kcal/mol for the cation radical and 11 kcal/mol for the anion radical. There exists no stable gauche-conformation in these molecules in contrast to neutral n-tetrasilane. It seems that the weakening of the central silicon-silicon bond on doping is connected to the concentration of the charge distributions on central silicon atoms with the change from trans- to cis-conformations in both n-tetrasilane cation and anion radicals. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62 : 393–401, 1997     

Probing the Chemical Functionalization of Single‐Walled Carbon Nanotubes with Multiple Carbon Ad‐Dimer Defects

Drying‐tube‐shaped single‐walled carbon nanotubes (SWCNTs) with multiple carbon ad‐dimer (CD) defects are obtained from armchair (n,n,m) SWCNTs (n=4, 5, 6, 7, 8; m=7, 13). According to the isolated‐pentagon rule (IPR) the drying‐tube‐shaped SWCNTs are unstable non‐IPR species, and their hydrogenated, fluorinated, and chlorinated derivatives are investigated. Interestingly, chemisorptions of hydrogen, fluorine, and chlorine atoms on the drying tube‐shaped SWCNTs are exothermic processes. Compared to the reaction energies for binding of H, F, and Cl atoms to perfect and Stone–Wales‐defective armchair (5,5) nanotubes, binding of F with the multiply CD defective SWCNTs is stronger than with perfect and Stone–Wales‐defective nanotubes. The reaction energy for per F₂ addition is between 85 and 88 kcal mol^?1 more negative than that per H₂ addition. Electronic structure analysis of their energy gaps shows that the CD defects have a tendency to decrease the energy gap from 1.98–2.52 to 0.80–1.17 eV. After hydrogenation, fluorination, and chlorination, the energy gaps of the drying‐tube‐shaped SWCNTs with multiple CD defects are substantially increased to 1.65–3.85 eV. Furthermore, analyses of thermodynamic stability and nucleus‐independent chemical shifts (NICS) are performed to analyze the stability of these molecules.     

Structure and stability of coinage metal fluoride and chloride clusters (MnFn and MnCln,M = Cu,Ag, or Au; n = 1–6)

Calculations in the framework of the density functional theory are performed to study the lowest‐energy isomers of coinage metal fluoride and chloride clusters (M_nF_n, M_nCl_n, M = Cu, Ag, or Au, n = 1–6). For all calculated species starting from the trimers the most stable structures are found to be cyclic arrangements. However, planar rings are favored in the case of metal fluorides whereas metal chlorides prefer nonplanar cycles. Calculated bond lengths and infrared frequencies are compared with the available experimental data. The nature of the bonding, involving both covalent and ionic contributions, is characterized. The stability and the fragmentation are also investigated. Trimers are found to be particularly stable when considering the Gibbs free energies. © 2012 Wiley Periodicals, Inc.     

Coordination of lithium ion with ethylene carbonate electrolyte solvent: A computational study

The coordination and energetics of low‐lying structures of [Li(EC)_n]⁺ have been analyzed by density functional theory (DFT) and polarizable continuum model (PCM) at the B3LYP/6‐311+G (d, p) level. The results show that the first shell around the lithium ion is fully occupied with four ethylene carbonate (EC) molecules in both gas phase and solvent. The examination on the contribution of vibration entropy to free energy of isomers of [Li(EC)_n]⁺ reveals that the stability of the best candidates at zero‐temperature cannot be maintained at finite temperatures due to the effects of their vibration entropy. In addition, structural transitions between the most stable four‐coordinated and the metastable three‐coordinated structure demand a very low energy barrier, suggesting that at a finite temperature the four‐coordinated and three‐coordinated isomers of [Li(EC)_n]⁺ can coexist in the EC organic solvent lithium salt electrolyte. © 2015 Wiley Periodicals, Inc.     

Multi‐zinc‐expanded graphene patches: Tetraradical versus diradical character

Three classes of multi‐Zn‐expanded graphene patches in different shapes are computationally designed through introducing a Zn chain into the corresponding middle benzenoid chain. Both density functional theory and complete active space self‐consistent field calculations predict that molecules of nnn‐quasi‐linear and nnn‐slightly bent series have the open‐shell broken‐symmetry (BS) singlet diradical ground states, whereas those of n(n+1)n species possess quintet tetraradical as their ground state and become open‐shell BS singlet tetraradicals when they are in a higher energy state. These results offer the first theoretical attempt to introduce multi‐Zn into the small graphene patches to form Zn‐expanded graphene patches, leading them to polyradical structures. This work provides an executable strategy to yield molecules which have stable polyradicaloid character and enhanced electronic properties of multi‐Zn‐expanded graphene patches. © 2012 Wiley Periodicals, Inc.     

Stability of cyclic (H2O)n clusters within molecular solids: Role of aromaticity

Cyclic water clusters (H₂O)_n (n = 3–12) trapped inside organic/inorganic hosts do not correspond to the global energy minimal structures. Their closed loop connections through the H‐bonds, although weakly interacting, result in diamagnetic ring currents leading to what we term “H‐bonded aromaticity.” Such H‐bonded aromaticity in supramolecular structures generalizes the formation of such stable (H₂O)_n molecules confined within various host systems. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Structure and energetic of Bn (n = 2–12) clusters: Electronic structure calculations

The electronic and geometric structures, total and binding energies, first and second energy differences, harmonic frequencies, point symmetries, and highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gaps of small and neutral B_n (n = 2–12) clusters have been investigated using density functional theory (DFT), B3LYP with 6‐311++G(d,p) basis set. Linear, planar, convex, quasi‐planar, three‐dimensional (3D) cage, and open‐cage structures have been found. None of the lowest energy structures and their isomers has an inner atom; i.e., all the atoms are positioned at the surface. Within this size range, the planar and quasi‐planar (convex) structures have the lowest energies. The first and the second energy differences are used to obtain the most stable sizes. A simple growth path is also discussed with the studied sizes and isomers. The results have been compared with previously available theoretical and experimental works. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Analysis of Why Boron Avoids sp2 Hybridization and Classical Structures in the BnHn+2 Series

We performed global minimum searches for the B_nH_n+2 (n=2‐5) series and found that classical structures composed of 2c–2e B? H and B? B bonds become progressively less stable along the series. Relative energies increase from 2.9 kcal mol^?1 in B₂H₄ to 62.3 kcal mol^?1 in B₅H₇. We believe this occurs because boron atoms in the studied molecules are trying to avoid sp² hybridization and trigonal structure at the boron atoms, as in that case one 2p‐AO is empty, which is highly unfavorable. This affinity of boron to have some electron density on all 2p‐AOs and avoiding having one 2p‐AO empty is a main reason why classical structures are not the most stable configurations and why multicenter bonding is so important for the studied boron–hydride clusters as well as for pure boron clusters and boron compounds in general.     

Influence of the alkyl chain length of some mesogenic molecules on their Langmuir film formation ability

Langmuir films of members of two homologous series, the 4‐n‐alkyl‐4′‐cyanobiphenyls (nCB) for n = 2–14 and trans‐4‐n‐alkyl(4′‐cyanophenyl)cyclohexanes (PCHn) for n = 2–12, have been studied by recording surface pressure/area isotherms and by Brewster angle microscopy. It has been found that the compounds with very short chains (n3) and very long chains (n>12 for nCB, n>10 for PCHn) are unable to form compressible monolayers at the air–water interface. Other members of both series can form stable Langmuir films, but both their rigidity and stability as well as the molecular packing vary with the alkyl chain length. The isotherms and BAM images imply that the organization of the liquid crystal molecules in the films is to some extent correlated with their ability to form corresponding mesophase in the bulk: nematogenic compounds tend to form rounded droplet‐like domains, whereas smectogenic compounds tend to form flat domains.     

Theoretical Investigation on SERS of Pyridine Adsorbed on Cn Clusters Induced by Charge Transfer: A Hint that SERS Could be Applied on Many Materials

The SERS spectra of pyridine–C_n (n=1–6) complexes are investigated theoretically. The obtained enhancement factors of about 10²–10³ in the pre‐resonance Raman spectrum calculations are attributed to charge‐transfer transitions from the carbon clusters to pyridine, where a good match of band structures between substrates and probe molecules is essential.     

Ab Initio MP2 and Density Functional Theory Computational Study of AcAlaNH2 Peptide Hydration: A Bottom‐Up Approach

AcAlaNH₂?n H₂O (n=1–13) complexes have been proposed as models to account for water solvent effects on the molecular properties of N‐acetyl‐L ‐alanine amide. Ab initio computations are planned to evaluate peptide–water interactions and to provide a means for approximating relative effects of the short‐range many‐body interactions arising in real solution without introducing any external parameters intended to quantify empirical or semiempirical potential‐energy functions. The present bottom‐up approach reveals the formation of compact ring clusters of water molecules strongly bonded to peptidic polar groups throughout hydrogen bonds. The explicit coordination of water molecules around the peptide renders the fully extended (FE) and polyproline II (PPII) conformers more stable with respect to the 3₁₀ helix or γ turn. The alternance of donor and acceptor groups on both sides of the FE and PPII conformers allows for synergy and extensive H‐bonding.     

Far‐Infrared Spectra of Yttrium‐Doped Gold Clusters AunY (n=1–9)

The geometric, spectroscopic, and electronic properties of neutral yttrium‐doped gold clusters Au_nY (n=1–9) are studied by far‐infrared multiple photon dissociation (FIR‐MPD) spectroscopy and quantum chemical calculations. Comparison of the observed and calculated vibrational spectra allows the structures of the isomers present in the molecular beam to be determined. Most of the isomers for which the IR spectra agree best with experiment are calculated to be the energetically most stable ones. Attachment of xenon to the Au_nY cluster can cause changes in the IR spectra, which involve band shifts and band splittings. In some cases symmetry changes, as a result of the attachment of xenon atoms, were also observed. All the Au_nY clusters considered prefer a low spin state. In contrast to pure gold clusters, which exhibit exclusively planar lowest‐energy structures for small sizes, several of the studied species are three‐dimensional. This is particularly the case for Au₄Y and Au₉Y, while for some other sizes (n=5, 8) the 3D structures have an energy similar to that of their 2D counterparts. Several of the lowest‐energy structures are quasi‐2D, that is, slightly distorted from planar shapes. For all the studied species the Y atom prefers high coordination, which is different from other metal dopants in gold clusters.     

Dynamic Odd–Even Effect in Liquid n‐Alkanes near Their Melting Points

n‐Alkanes are the textbook examples of the odd–even effect: The difference in the periodic packing of odd‐ and even‐numbered n‐alkane solids results in odd–even variation of their melting points. However, in the liquid state, in which this packing difference is not obvious, it seems natural to assume that the odd–even effect does not exist, as supported by the monotonic dependence of the boiling points of n‐alkanes on the chain length. Herein, we report a surprising odd–even effect in the translational diffusional dynamic properties of n‐alkanes in their liquid states. To measure the dynamics of the molecules, we performed quasi‐elastic neutron scattering measurements near their melting points. We found that odd‐numbered n‐alkanes exhibit up to 30 times slower dynamics than even‐numbered n‐alkanes near their respective melting points. Our results suggest that, although n‐alkanes are the simplest hydrocarbons, their dynamic properties are extremely sensitive to the number of carbon atoms.     

Structures and bonding patterns of nanoannular carbon clusters (C4–C20) through AIM analyses

Structures, binding energies, harmonic frequencies, dipole moments, HOMO–LUMO energy gaps and particularly atoms in molecules (AIM) analyses of some nanoannular carbon clusters (C₄–C₂₀) are investigated at B3LYP/6-31+G(d) level of theory. No correlation is found by plotting the calculated binding energies as a functional number of carbon atoms of carbon clusters. The calculated binding energies sharply increase from C₄ to C₁₀ while slowly from C₁₀ to C₂₀. The binding energies of C_4n+2 clusters including C₆, C₁₀, C₁₄, and C₁₈ have a clear increase when compared with others indicating their aromatic characters which is confirmed by results of HOMO–LUMO energy gaps and geometrical parameters. AIM analyses show that most of our carbon clusters are topologically normal (non-conflict) with stable structures. Nevertheless, the topological networks of small antiaromatic rings, C₄ and C₈, at their equilibrium geometries may change via molecular vibrations. The existence of straight bond paths in 3D molecular graphs of carbon clusters with n > 10 implies that ring strains are decreased as the ring sizes grow. Except for C₄ and C₈, the ellipticity values for the remaining carbon clusters are small indicating that the C–C bond is conserved in these clusters. Dipole moments of even-numbered structures are negligible, whereas odd-numbered ones have μ values of 0.09−0.73 D.