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The first thorough theoretical mechanism analysis of heteronuclear bimetallic cation NiAl + with cyclohexane has been investigated on singlet and triplet potential energy surfaces (PESs) by using density functional theory. Our calculated results show that NiAl + can assist in the decomposition of cyclohexane to form benzene through two types of reaction channel: C H bond activation and H 2 formation; C C bond activation and HD formation. The most important conclusion is that NiAl + exhibits high efficiency and also high regioselectivity for C H bond oxidation. However, the high zero-point vibrational energy (ZPVE) value for the cleavage of inert C C bond is also the origin of its failure to form HD. In the process of the first C H and C C bond activations, crossing points (CPs) have been appeared between the two adiabatic surfaces, respectively. The minimum energy crossing points (MECPs) are gotten using the algorithmin Harvey method. Density of states (DOS) is used to obtain a deeper understanding for the roles of the front molecular orbital of the initial complexes. The bonding properties of the special intermediates involved in the process of C C bond activations are discussed by the IR spectrum methods. [ABSTRACT FROM AUTHOR]

In this paper, the reaction mechanism for N 2 O with CO on the surface of Ni 5 cluster was investigated by the B3LYP method of density functional theory (DFT). Ni atom of various species was calculated using B3LYP/ LANL2DZ basis set, and C, N, O atoms at B3LYP/6-31G ∗ level. In the temperature range of 100–1000 K, the statistical thermodynamics and Eyring transition state theory with Winger correction were used to study the kinetic characters of reaction. The calculation results indicated that the reaction of N 2 O with CO on Ni 5 cluster had two major reacting processes: (1) O atom first dissociated from N 2 O on Ni 5 cluster, and then reacted with CO on Ni 5 and (2) on the surface of Ni 5 catalyst, O atom of N 2 O direct interacted with C atom of CO, resulting into the dissociation of N 2 O and the form of CO 2 . The direct O extraction channel was the main channel due to its low potential energy and high rate constant. [ABSTRACT FROM AUTHOR]

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Highlights: [•] We studied the gas-phase activation of methane by (n =1−3). [•] There is only one crossing point (CP) and minimum energy crossing point (MECP) on the three system, respectively. [•] The active center in the reaction of with methane include only one metal atom. [•] The product of with methane is hydrogen-bridge bond molecule. [•] For (n =1−3) with the increase of the metal atoms, the activation of methane C–H bonds rise sharply. [ABSTRACT FROM AUTHOR]

A systematic investigation on the H‐abstraction reactions of 8 carbene radical anions with CCl3H has been performed theoretically using the popular DFT functional BHandHLYP/aug‐cc‐pVTZ/RECP level of theory. As a result, our studies strongly suggest that the reactivity of the title reactions (CX1X2•− + CCl3H) present increase in the order: CHI•− < CHBr•− < CHCl•− < CHF•− for first halogen CHX•− and CCI2•− < CBr2•− < CCl2•− < CF2•− for second halogen CX2•−, more important, the reactions of the former exhibit more activity than those of corresponding the latter. Moreover, based on the NBO analysis, the Activation Strain model analysis and the correlations analyses of activation barrier with both PA and IE, respectively, we further confirm over the conclusion. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: A computational study of the [2+2] cycloaddition reaction pathways for formaldehyde–ketene and formaldehyde–isocyanic acid has been presented by using the DFT(B3LYP) method. These cycloaddition reactions could yield to eight different four-membered molecules. In the two considered reactions, the reactions for the β-propiolactone and oxazetidinone products have the lower barriers of 26.40 and 32.88kcalmol−1 and are exothermic by 27.68 and 4.00kcalmol−1, respectively. The β-propiolactone and oxazetidinone ring compounds have been predicted to be the most stable thermodynamically. Simulation of the solvent environment (toluene, THF, acetone, acetonitrile and water) has been investigated by using polarized continuum model method, yet only small differences have been found to occur in energetics between the studied structures in the gas-phase and in the solvent. [Copyright &y& Elsevier]

• The mechanism of HER on Mo-Edge with the unsaturated Mo and S were investigated. • The H 2 evolution reaction mainly occurred on Mo U. • The formation of molybdenum hydride (Mo U -H) was the rate-limiting step. In this paper, the mechanisms of H 2 evolution over the Mo-Edge of 2H-MoS 2 with the unsaturated Mo (Mo U) and S (S U) were investigated by the density functional theory. The calculations indicated that Mo U was a key active site for H 2 evolution. In the process of H 2 evolution, the S U firstly absorbed H atom by the Volmer reaction, which caused the aggregation of electron on Mo U , resulting in the barriers reduction of H transfer and H 2 evolution on Mo U. The formation of molybdenum hydride was the rate-limiting step. Compared to Mo-edge in 2H-MoS 2 , the barrier of key step for H 2 evolution on Mo-edge with S U and Mo U decreased obviously. This implied that the removal fractional S from the Mo-edge of 2H-MoS 2 could enhance its H 2 evolution activity and the electron trapping ability of active site for H 2 evolution by the Volmer-Heyrovsky reaction might affect its activity. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations have been carried out to explore the underlying origin of merits for rigid π-spacer based on reference dyes C255 and C254 . The results demonstrate that higher short-circuit current density ( J SC ) of C255 is primarily ascribed to the lower EBE , while the biggish short-circuit current density ( V OC ) mainly originates from the larger μ normal compared to C254 . Besides, a novel index integral of overlap between hole and electron ( S ) is firstly introduced to quantitatively estimate the facility of intramolecular charge transfer (ICT) and preliminarily confirmed to be effective for the research target of this work. Furthermore, three series of dyes (C-series, A-series, AC-series) have been designed and characterized to screen promising sensitizer candidates and design strategies, while delightful results have been achieved including 6 promising candidates, design stratagem on efficiently reducing the charge recombination and combinational tactics on screening new dyes with excellent spectral properties or outstanding DSSC performance. [ABSTRACT FROM AUTHOR]

Abstract: The mechanisms for the abstraction reactions of germylenes with oxirane and thiirane have been characterized in detail using density functional theory. All the stationary points were determined at the B3LYP/6-311++G (d, p) level of the theory. As a result, our theoretical investigations suggest that, irrespective of deoxygenation and desulfurization, the alkyl-substituted germylene abstractions are much more favorable than those of the π-donor-substituted germylenes. Moreover, for a given germylene, the desulfurization reaction is more exothermic as well as more kinetically favorable. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. A comparison with carbene and silylene also led to the same result and the results obtained allowed a number of predictions to be made. [Copyright &y& Elsevier]

Abstract: The reactivity of X(3P) (X=Ge, Sn, Pb) with N2O(X1Σ) on both singlet and triplet potential energy surfaces have been investigated at the B3LYP level of theory. To accurately evaluate the activation barrier and reaction energy, the coupled cluster single point calculations using the B3LYP structures is performed. The calculated results are in good agreement with experimental observations. The (X=Ge, Sn, and Pb) reactions that Arthur Fontijn has been observed are spin-forbidden for formation of ground state products in the experiments. The present paper is discussed with the aid of the direct abstraction (DA) mechanism (also called the surface crossing model), a correlation argument based on separated fragments X+O+N2 can explain the inefficiency of the (X=Ge, Sn, and Pb) reactions at 298K by the need to switch electron configurations along low-energy adiabatic paths from ground-state reactants to energetically accessible product states. [Copyright &y& Elsevier]

In this paper, the mechanisms of H 2 evolution on Pt 6 , Pt 5 Sn 5 , and Pt 3 Sn 6 clusters were respectively investigated by the B3LYP method of density functional theory (DFT). The B3LYP functional with non-local dispersion corrections (B3LYP-D3) method were performed to investigate the adsorption of H and H + on clusters. The calculation results indicated that the adsorption energy of H on Pt reduced due to the interaction of Sn and Pt, which promoted H desorption from Pt to form H 2 . Meanwhile, Sn atom of Pt 5 Sn 5 and Pt 3 Sn 6 clusters had strong interaction with H + due to the existence of Pt, which was benefit for the reduction of H + on Sn atom. As a consequence, Pt 5 Sn 5 and Pt 3 Sn 6 showed lower potential barrier and higher activities than Pt for H 2 evolution. The potential barriers of H 2 formation over Pt 3 Sn 6 clusters was only 11.1% of that over Pt cluster. [ABSTRACT FROM AUTHOR]

Abstract: Series sensitizers of indoline and triphenylamine as the donor group, quinoxaline and its derivatives as the additional acceptor, different heteroaromatic rings (furan, benzene and selenophene) as the π-conjugated group, 2-cyanoacrylic acid as the acceptor/anchoring which featured on the D–A–π–A architecture have been theoretically designed based on the reported dyes IQ2 and TQ2 used in dye-sensitized solar cells (DSSCs), to shed light on how the additional (auxiliary) acceptor and π spacer influence the performance of the dyes. These enable us to determine master factors influenced the efficiency of DSSCs, such as the light-harvesting efficiency, lifetime of excited state, exciton binding energy, total reorganization energy and electron injection driving force as well as the vertical dipole moment. The theoretical results revealed that compared with dye IQ2, our designed dyes IQS2 and IQS3 displayed much better light harvesting properties and longer first excited lifetime. [Copyright &y& Elsevier]