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Lu Wang Jijun Zhao Zhen Zhou S. B. Zhang Zhongfang Chen 《Journal of computational chemistry》2009,30(15):2509-2514
Inspired by the concept of superatom via substitutionally doping an Al13 magic cluster, we investigated the H2 molecule dissociation on the doped icosahedral Al12X (X = B, Al, C, Si, P, Mg, and Ca) clusters by means of density functional theory. The computed reaction energies and activation barriers show that the concept of superatom is still valid for the catalysis behavior of doped metal clusters. The hydrogen dissociation behavior on metal clusters characterized by the activation barrier and reaction energy can be tuned by controllable doping. Thus, doped Al12X clusters might serve as highly efficient and low‐cost catalysts for hydrogen dissociation. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009 相似文献
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Dr. Israel Fernández Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Fernando P. Cossío 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12395-12403
To understand the factors that control the activation barrier of type‐I 1,2‐dyotropic reactions (X‐EH2‐CH2‐X*→X*‐EH2‐CH2‐X, with E=C and Si, X=H, CH3, SiH3, F to I) and trends therein as a function of the migrating groups X, we have explored ten archetypal model reactions of this class using relativistic density functional theory (DFT) at ZORA‐OLYP/TZ2P. The main trends in reactivity are rationalized using the activation strain model of chemical reactivity, which had to be extended from bimolecular to unimolecular reactions. Thus, the above type‐I dyotropic reactions can be conceived as a relative rotation of the CH2CH2 and [X???X] fragments in X‐CH2‐CH2‐X. The picture that emerges from these analyses is that reduced C? X bonding in the transition state is the origin of the reaction barrier. Also the trends in reactivity on variation of X can be understood in terms of how sensitive the C? X interaction is towards adopting the transition‐state geometry. A valence bond analysis complements the analyses and confirms the picture emerging from the activation strain model. 相似文献
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Vlasta Bona
i-Koutecký Roland Mitri Christian Bürgel Melanie Nßler 《Chemical physics》2008,350(1-3):111
We present a theoretical study of the ultrafast dynamics in noble metal clusters interacting with molecular oxygen which is of fundamental importance for the understanding and design of cluster-based heterogenous nanocatalysts. We demonstrate that intrinsic dynamical properties can significantly promote the reactivity of small noble metal clusters towards O2. This concept is illustrated by performing collision simulations between and clusters and O2 in the framework of the ab initio molecular dynamics (MD) using density functional theory (DFT). We show that different nature and efficiency of the internal vibrational energy redistribution (IVR) during the collisions with O2 are responsible for considerably different sticking probabilities of O2 to silver and gold clusters, respectively. In the case of , resonant IVR between the cluster and the O2 subunit activates the O–O bond and promotes the subsequent oxidation reaction. In contrast, in the case of fast dissipative IVR on the time scale of 1 ps leads to a higher sticking probability for O2 but the O–O bond is very rapidly deactivated and cannot participate in further oxidation processes. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters. Such different behaviour of silver and gold clusters colliding with O2 originates from difference in relativistic effects which are considerably more pronounced in the case of gold clusters causing more directional rigid bonding in contrast to silver clusters with more s-metallic floppy character. Moreover, we demonstrate that breaking of O–O bond can be induced in by a selective excitation of the O–O bond with an ultrashort pulse in the infrared spectral range. This opens the perspective to control the action of nanocatalysts by employing shaped laser pulses and thus bridges the fields of femtochemistry and cluster nanocatalysis. 相似文献
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Computational Study of the Interactions between Benzene and Crystalline Ice Ih: Ground and Excited States
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Dr. Divya Sharma Dr. W. M. C. Sameera Dr. Stefan Andersson Prof. Gunnar Nyman Prof. Martin J. Paterson 《Chemphyschem》2016,17(24):4079-4089
Ground‐state geometries of benzene on crystalline ice cluster model surfaces (Ih) are investigated. It is found that the binding energies of benzene‐bound ice complexes are sensitive to the dangling features of the binding sites. We used time‐dependent DFT to study the UV spectroscopy of benzene, ice clusters, and benzene–ice complexes, by employing the M06‐2X functional. It is observed that the size of the ice cluster and the dangling features have minor effects on the UV spectral characteristics. Benzene‐mediated electronic excitations of water towards longer wavelengths (above 170 nm) are noted in benzene‐bound ice clusters, where the cross‐section of photon absorption by water is negligible, in good agreement with recent experimental results (Thrower et al., J. Vac. Sci. Technol. A, 2008, 26 , 919–924). The intensities of peaks associated with water excitations in benzene–ice complexes are found to be higher than in isolated ice clusters. The π→π* electronic transition of benzene in benzene–ice complexes undergoes a small redshift compared with the isolated benzene molecule, and this holds for all benzene‐bound ice complexes. 相似文献
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The oxidation of carbon monoxide (CO) is important for a series of technological and environmental applications. In this work, the catalytic oxidation of CO on Si-doped (6,0) boron nitride nanotubes (BNNTs) is investigated by using density functional theory calculations. Reaction barriers and corresponding thermodynamic parameters were calculated using the M06-2X, B3LYP and wB97XD density functionals with 6-31G* basis set. Our results indicate that a vacancy defect in BNNT strongly stabilizes the Si adatom and makes it more positively charged. This charging enhances the adsorption of reaction gases (O2 and CO) and results in the change of the electronic structure properties of the tube. The calculated barrier of the reaction CO + O2 → CO2 + Oads on Si-doped BNNTs following the Langmuir–Hinshelwood is lower than that on the traditional noble metal catalysts. The second step of the oxidation would be the Eley–Rideal reaction (CO + Oads → CO2) with an energy barrier of about 1.8 and 10.1 kcal/mol at M06-2X/6-31G* level. This suggests that the CO oxidation catalyzed by the Si-doped BNNTs is likely to occur at the room temperature. The results also demonstrate that the activation energies and thermodynamic quantities calculated by M06-2X, B3LYP and wB97XD functionals are consistent with each other. 相似文献
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Yaxia Qiao Lingling Xu Hao Zhang Hongjian Luo 《Surface and interface analysis : SIA》2021,53(1):46-52
The O2 adsorption and dissociation on M‐doped (M = Cu, Ag, W) Al(111) surface were studied by density functional theory. The adsorption energy of adsorbate, the average binding energy and surface energy of Al surface, and the doping energy of doping atom were calculated. All the doped atoms can be stably combined with Al atoms, while being slightly embedded in the surface to a certain depth. The TOP‐type surfaces are the most stable doped surfaces for O2 adsorption, which is related to the orbital hybridization between the adsorbate and the surface atoms, the electronegativity, and the orbital energy level of the doping atoms. Moreover, the O atoms and doping atoms contribute significantly to the density of states (DOS), especially the O‐p orbital electrons and the d orbital electrons of doping atoms. The degree of O2 dissociation is related to the doping atoms on Al surfaces, and the doping atoms actually resist the dissociation of O2. W atoms have the best resistance effect on the O2 dissociation as compared with Cu and Ag atoms, especially W‐1NN surface, which has both large barrier energy and reaction energy. 相似文献
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Yan‐Ping Ma Dr. Xun‐Lei Ding Dr. Yan‐Xia Zhao Sheng‐Gui He Prof. Dr. 《Chemphyschem》2010,11(8):1718-1725
Density functional theory (DFT) calculations are used to investigate the reaction mechanism of V3O8+C2H4. The reaction of V3O8 with C2H4 produces V3O7CH2+HCHO or V3O7+CH2OCH2 overall barrierlessly at room temperature, whereas formation of hydrogen‐transfer products V3O7+CH3CHO is subject to a tiny overall free energy barrier (0.03 eV), although the formation of the last‐named pair of products is thermodynamically more favorable than that of the first two. These DFT results are in agreement with recent experimental observations. The (Ob)2V(OtOt). (b=bridging, t=terminal) moiety containing the oxygen radical in V3O8 is the active site in the reaction with C2H4. Similarities and differences between the reactivities of (Ob)2V(OtOt). in V3O8 and the small VO3 cluster [(Ot)2VOt.] are discussed. Moreover, the effect of the support on the reactivity of the (Ob)2V(OtOt). active site is evaluated by investigating the reactivity of the cluster VX2O8, which is obtained by replacing the V atoms in the (Ob)3VOt support moieties of V3O8 with X atoms (X=P, As, Sb, Nb, Ta, Si, and Ti). Support X atoms with different electronegativities influence the oxidative reactivity of the (Ob)2V(OtOt). active site through changing the net charge of the active site. These theoretical predictions of the mechanism of V3O8+C2H4 and the effect of the support on the active site may be helpful for understanding the reactivity and selectivity of reactive O. species over condensed‐phase catalysts. 相似文献
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Dr. Zhen Guo Dr. Xiangguo Guan Dr. Jie‐Sheng Huang Dr. Wai‐Man Tsui Prof. Dr. Zhenyang Lin Prof. Dr. Chi‐Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11320-11331
The X‐ray crystal structure of [RuVI(NMs)2(tmp)] (Ms=SO2‐ p‐MeOC6H4; tmp=5,10,15,20‐tetramesitylporphyrinato(2?)), a metal sulfonylimide complex that can undergo alkene aziridination and C? H bond amination reactions, shows a Ru?N distance of 1.79(3) Å and Ru‐N‐S angle of 162.5(3)°. Density functional theory (DFT) calculations on the electronic structures of [RuVI(NMs)2(tmp)] and model complex [RuVI(NMs)2(por0)] (por0=unsubstituted porphyrinato(2?)) using the M06L functional gave results in agreement with experimental observations. For the amination of ethylbenzene by the singlet ground state of [RuVI(NMs)2(por0)], DFT calculations using the M06L functional revealed an effectively concerted pathway involving rate‐limiting hydrogen atom abstraction without a distinct radical rebound step. The substituent effect on the amination reactivity of ethylbenzene by [RuVI(NX)2(por0)] (X=SO2‐p‐YC6H4 with Y=MeO, Me, H, Cl, NO2) was examined. Electron‐withdrawing Y groups lower the energy of the LUMOs of [RuVI(NX)2(por0)], thus facilitating their interaction with the low‐lying HOMO of the ethylbenzene C? H bond and hence increasing the reactivity of [RuVI(NX)2(por0)]. DFT calculations on the amination/aziridination reactions of [RuVI(NSO2C6H5)2(por0)] with pent‐4‐enal, an aldehyde substrate bearing acyl, homoallylic, and allylic C? H bonds and a C?C bond, revealed a lower reaction barrier for the amination of the acyl C? H bond than for both the amination of the other C? H bonds and aziridination of the C?C bond in this substrate. 相似文献
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《Journal of computational chemistry》2017,38(25):2186-2192
O O bond homolysis in hydrogen peroxide (H2O2) has been studied using theoretical methods of four conceptually different types: hybrid DFT (B3LYP, M06‐2X), double‐hybrid DFT (B2‐PLYP), coupled‐cluster (CCSD(T)), and multiconfigurational (CASPT2). In addition, the effects of basis set size have also been analyzed. For all of these methods, the O O bond homolysis in hydrogen peroxide has been found to proceed through hydrogen bonded radical pair complexes. Reaction barriers for collapse of the radical pairs to hydrogen peroxide are minute, leading to an overall very flat potential energy surface. However, hydrogen bonding energies in the radical pair complex expressed as the energy difference to two separate hydroxyl radicals are sizeable and exceed 10 kJ/mol for all theoretical methods considered in this study. © 2017 Wiley Periodicals, Inc. 相似文献
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采用密度泛函理论(DFT)中广义梯度近似(GGA)方法, 对Pt原子与γ-Al2O3(001)面的相互作用及迁移性能进行了研究. 分析了各种可能吸附位及吸附构型的松弛和变形现象, 吸附能和迁移能垒的计算结果表明: Pt团簇能够稳定吸附在该表面. Pt原子在表面O位的吸附能明显较高, 这主要是由Pt向基底O原子转移了电子所致. 电荷布居分析表明, Pt原子显电正性, Pt和Al原子之间存在排斥作用, 导致与Al原子产生较弱相互作用. 计算的平均吸附能大小依赖于Pt团簇的大小和形状, 总体趋势是随着Pt原子数增多, 吸附能降低. Pt原子在γ-Al2O3(001)表面迁移过程所需克服的迁移能垒最高值为0.51 eV. 随着吸附的Pt原子数增多,更倾向于形成Pt团簇. 因此, Pt原子在γ-Al2O3(001)表面的吸附演变不可能形成光滑、均匀平铺的吸附构型, 而在一定条件下容易出现团聚. 相似文献
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Hsueh‐Chien Li Jeng‐Da Chai Ming‐Kang Tsai 《International journal of quantum chemistry》2014,114(12):805-812
In this study, 12 bound complexes were selected to construct a database for testing 15 dispersion‐improved exchange‐correlation (XC) functionals, including hybrid generalized gradient approximation (GGA), modified using the Grimme's pairwise strategy, and double hybrid XC functionals, for specifically characterizing the CO2 binding by alcoholamines. Bound complexes were selected based on the characteristics of their hydrogen bonds, dispersion, and electrostatic (particularly between the positive charge of CO2 and the lone pair of N of alcoholamines) interactions. The extrapolated binding energy from the aug‐cc‐pVTZ (ATZ) to aug‐cc‐pVQZ (AQZ) basis set at the CCSD(T)/CBS(MP2+DZ) level was used as the reference for the XC functional comparison. M06‐2X produced the optimal agreement if the optimized geometries at MP2/ATZ level were chosen for all the test bound complexes. However, M06‐L, ωB97X, and ωB97, and were preferred if the corresponding density functional theory (DFT) optimized geometries were adapted for the benchmark. Simple bimolecular reaction between CO2 and monoethanolamine simulated using polarizable continuum solvation model confirmed that ωB97, ωB97X, and ωB97XD qualitatively reproduced the energetics of MP2 level. The inconsistent performance of the tested XC functionals, observed when using MP2 or DFT optimized geometries, raised concerns regarding using the single‐point ab initio correction combined with DFT optimized geometry, particularly for determining the nucleophilic attack by alcoholamines to CO2. © 2014 Wiley Periodicals, Inc. 相似文献
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Reducing the Cost and Preserving the Reactivity in Noble‐Metal‐Based Catalysts: Oxidation of CO by Pt and Al–Pt Alloy Clusters Supported on Graphene
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Dr. Kenichi Koizumi Prof. Katsuyuki Nobusada Prof. Mauro Boero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5181-5188
The oxidation mechanisms of CO to CO2 on graphene‐supported Pt and Pt‐Al alloy clusters are elucidated by reactive dynamical simulations. The general mechanism evidenced is a Langmuir–Hinshelwood (LH) pathway in which O2 is adsorbed on the cluster prior to the CO oxidation. The adsorbed O2 dissociates into two atomic oxygen atoms thus promoting the CO oxidation. Auxiliary simulations on alloy clusters in which other metals (Al, Co, Cr, Cu, Fe, Ni) replace a Pt atom have pointed to the aluminum doped cluster as a special case. In the nanoalloy, the reaction mechanism for CO oxidation is still a LH pathway with an activation barrier sufficiently low to be overcome at room temperature, thus preserving the catalyst efficiency. This provides a generalizable strategy for the design of efficient, yet sustainable, Pt‐based catalysts at reduced cost. 相似文献
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Shuo Li J. R. Fried Jeremy Sauer John Colebrook Douglas S. Dudis 《International journal of quantum chemistry》2011,111(12):3212-3229
Quantum mechanics (QM) calculations, molecular dynamics (MD) simulations using the condensed‐phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field, and the atom‐centered density matrix propagation (ADMP) approach have been used to investigate properties of phosphoric acid (PA). QM using B3LYP/6‐31++G(d,p) density functional theory were used to calculate gas‐phase proton affinities and interaction energies of PA and its derivatives. Detailed single coordinate driving, followed by quadratic synchronous transit optimization was used to determine energy barriers for different proton transfer (PT) pathways. Determined energy barrier heights in ascending order are (unit: kJ/mol): H3O+→H3PO4 (0); H4P2O7→H3PO4 (2.61); H3PO4→H2PO (5.31); H4PO→H3PO4 (~7.33); H3PO4→H4P2O7/H3PO4→H3PO4 (15.99); H4P2O7→H2O (28.61); H3PO4→H2O (47.14). The COMPASS force field was used to study condensed‐phase properties of PA. Good agreement between experimental data and MD results including density, radial distribution functions, and self‐diffusion coefficient at different temperatures provides validation of the COMPASS force field for PA. Finally, preliminary ADMP studies on a cluster of three PA molecules shows that the ADMP approach can reasonably describe the PT and self‐dissociation processes in PA. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
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Alan Miralrio Luis Enrique Sansores 《International journal of quantum chemistry》2014,114(14):931-942
The electronic structure and stability in binary and ternary aluminum‐bismuth‐nitrogen nanoclusters up to six atoms are studied using density functional theory (DFT). The lowest energy geometries were obtained by sampling the geometrical space with a Monte Carlo method and geometry optimizations, at DFT level, with M06L functional. The clusters stability is analyzed using formation and fragmentation energies. Our results show that a high concentration of nitrogen presents a tendency to form nitrogen clusters. highest occupied molecular orbital‐lowest unoccupied molecular orbital gaps show the well‐known oscillation as the number of atoms is increased. Bonding between Al, Bi, and N has mainly a π character. Bismuth and aluminum atoms tend to promote high multiplicity states in small clusters. These new binary and ternary materials provide a potential new field in optoelectronics and high energetic material compounds. © 2014 Wiley Periodicals, Inc. 相似文献