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1.
ABSTRACT

The nanomaterials based on the In2O3 molecule are widely used as catalysts and sensors among other applications. In the present study, we discuss the possibility of using nanoclusters of In2O3 as molecular photomotors. A comparative analysis of the electronic structure of the In2O3 molecule in the free state and in the crystal is performed. For the free In2O3 molecule the geometry of its lowest structures, V-shape and linear, was optimised at the CCSD(T) level, which is the most precise computational method applied up to date to study In2O3. Using experimental crystallographic data, we determined the geometry of In2O3 in the crystal. It has a zigzag, not symmetric structure and possesses a dipole moment with magnitude slightly smaller than that of the V-structure of the free molecule (the linear structure due to its symmetry has no dipole moment). According to the Natural Atomic population analysis, the chemical structure of the linear In2O3 can be represented as O = In?O?In = O; the V-shaped molecule has the similar double- and single-bond structure. The construction of nanoclusters from ?bricks? of In2O3 with geometry extracted from crystal (or nanoclusters extracted directly from crystal) and their use as photo-driven molecular motors are discussed.  相似文献   

2.
Despite the fact that B3O is the second simplest B n O radical after BO, a controversy recently emerged concerning the molecular structure of its global minimum. Two recent theoretical groups predicted the linear quartet BBBO to be the ground isomer. By contrast, another recent theoretical group reported that B3O has a doublet B3-ring ground structure. Moreover, larger B n O clusters usually have low-lying B3-ring isomers. In order to determine the accurate energetic competition between linear and cyclic structures in both the doublet and quartet, and to understand the detailed isomerism between various isomers, which is vital for understanding the formation mechanism of B3O, we report the first potential energy surface (PES) study of B3O at various computational levels, including CCSD(T)/6-311+G(2df), CCSD(T)/aug-cc-pVTZ, CCSD(T)/aug-cc-pVQZ and G3B3 for the single-point energy, as well as B3LYP/6-311+G(d) and QCISD/6-311+G(d) for geometrical optimisation. It is shown that the isomers in the quartet state are all thermodynamically more stable than the corresponding doublet ones, and on both the quartet and doublet PESs, the linear form has the lowest energy. Therefore, our study on both linear and cyclic isomers shows that the linear quartet BBBO 4 01 is definitively the ground isomer. Although being much less stable than the quartet linear BBBO global minimum by >20 kcal mol?1, five cyclic isomers exist as local minima, with the bi-cyclic structure 4 02 possessing the smallest barrier of around 15 kcal mol?1. The dissociation energies for direct combination processes B3 + O, B2 + BO and B + B2O are discussed. The present work may be helpful in obtaining a deep understanding of the doping and oxidation process of pure B n clusters.  相似文献   

3.
Ion-molecular interactions in the HCl-EtOH-H2O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H2O and EtOH molecules during the formation of the (H5C2(H)O…H…O(H)C2H5)+, (H2O…H…OH2)+, and (H2O…H…O(H)C2H5)+ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H2O mixtures, (H2O…H…OH2)+ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H2O…H…O(H)C2H5)+ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H5C2(H)O…H+…Cl?) uncharged complexes with the participation of the Cl? anion.  相似文献   

4.
Previous investigations have shown that it is difficult to acquire the infrared (IR) spectra of M+(H2O) (M?=?Cu, Au) using a single IR photon by attaching an Ar atom to M+(H2O). To explore whether the IR spectra can be obtained using the two Ar atoms tagging method, the geometrical structures, IR spectra and interaction energies are investigated in detail by ab initio electronic structure calculations for M+(H2O)Ar2 (M?=?Cu, Au) complexes. Two conceivable isomeric structures are found, which result from different binding sites for two Ar atoms. CCSD(T) calculations predict that two Ar atoms are most likely to attach to Cu+ for the Cu+(H2O)Ar2 complex, while the Au+(H2O)Ar2 complex prefers the isomer in which one Ar atom attaches to an H atom of the H2O molecule and the other one is bound to Au+. Moreover, the calculated binding energies of the second Ar atom are smaller than the IR photon energy, and so it is possible to obtain the IR spectra for both Cu and Au species. The changes in the spectra caused by the attachment of Ar atoms to M+(H2O) are discussed.  相似文献   

5.
本文提出了迭代的组态相互作用方法(IMRCI). IMRCI被用来计算H2O和CH2(单重态和三重态)在平衡态和远离平衡时的电子能量. IMRCI、MP2、MP3、MP4、CCSD和CCSD(T)还用来计算H2O、CH2(单重态和双重态)和N2的势能曲线. 这些计算结果表明IMRCI的结果不依赖初始的多参考态组态函数,并能较快地收敛到完全组态相互作用的计算结果. 相比完全组态相互作用的结果,仅需2至4次迭代,IMRCI的误差就能达到10-5 hartree数量级. 另外,IMRCI还提供了寻找势能面上主要电子组态的一个有效途径. 这将有助于单参考态和多参考态理论模型得到准确的计算结果.  相似文献   

6.
The mechanism and kinetics of the reaction of hydrogen sulphide (H2S(1A1)) with hydroperoxyl radical (HO2(2A″)) on the lowest doublet potential energy surface have been theoretically studied. The potential energy surface for possible pathways has been investigated by employing Complete Basis Set (CBS), DFT, and CCSD(T) methods. Three possible pathways are suggested for the title reaction. The most probable entrance channel consists of formation of a hydrogen-bonded pre-reaction complex (vdw1) and two energised intermediates. Multichannel RRKM-Steady State Approximation and CVT calculations have been carried out to compute the rate constants over a broad range of temperature from 200?K to 3000?K to cover the atmospheric and combustion conditions and pressure from 0.1 to 2000?Torr. No sign of pressure dependence was observed for the title reaction over the stated range of pressure. We have shown that the major products of the title reaction are H2O2 and SH while at higher temperatures, formation of the other products such as H2O, HOS, HSOH and OH are feasible, too. Our calculated overall rate constant is in agreement with the reported experimental data in the literature.  相似文献   

7.
A detailed computational study has been performed at the QCISD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) level for the NCO with CH3 reaction by constructing singlet and triplet potential energy surfaces (PES). The results show that the title reaction is more favorable for the singlet PES than the triplet PES. On the singlet PES, the dominant channel is the barrierless addition of the O or N atom to the C atom of the methyl group to form CH3NCO (IM1) and CH3OCN (IM2). On the triplet PES, the favorable channel is the barrierless addition of the N atom to the C atom of the methyl group to form an intermediate CH3NCO (3IM2), which then undergoes a N–C bond scission process to give out CH3N + CO.  相似文献   

8.
Li Wang  Na Wang  Hongqing He 《Molecular physics》2014,112(11):1600-1607
The reaction mechanisms of methylhydrazine (CH3NHNH2) with O(3P) and O(1D) atoms have been explored theoretically at the MPW1K/6-311+G(d,p), MP2/6-311+G(d,p), MCG3-MPWPW91 (single-point), and CCSD(T)/cc-pVTZ (single-point) levels. The triplet potential energy surface for the reaction of CH3NHNH2 with O(3P) includes seven stable isomers and eight transition states. When the O(3P) atom approaches CH3NHNH2, the heavy atoms, namely N and C atoms, are the favourable combining points. O(3P) atom attacking the middle-N atom in CH3NHNH2 results in the formation of an energy-rich isomer (CH3NHONH2) followed by migration of O(3P) atom from middle-N atom to middle-H atom leading to the product P6 (CH3NNH2+OH), which is one of the most favourable routes. The estimated major product CH3NNH2 is consistent with the experimental measurements. Reaction of O(1D) + CH3NHNH2 presents different features as compared with O(3P) + CH3NHNH2. O(1D) atom will first insert into C–H2, N1–H4, and N2–H5 bonds barrierlessly to form the three adducts, respectively. There are two most favourable paths for O(1D) + CH3NHNH2. One is that the C–N bond cleavage accompanied by a concerted H shift from O atom to N atom (mid-N) leads to the product PI (CH2O + NH2NH2), and the other is that the N–N bond rupture along with a concerted H shift from O to N (end-N) forms PIV (CH3NH2 + HNO). The similarities and discrepancies between two reactions are discussed.  相似文献   

9.
ABSTRACT

In this work, four different channels, represented by H2O???HO2 + HOCl, HO2???H2O + HOCl, H2O???HOCl + HO2 and HOCl???H2O + HO2 have been analysed for water-catalysed formations of H2O2 + ClO to gain insight into the potential impact of the reaction in the atmosphere. The results at the CCSD(T)/aug-cc-pVTZ//MP2/6-311+G(2df,2p) level show that the H2O???HO2 + HOCl reaction is kinetically the most favourable channel among the four channels. Compared to the channel of H2O2 + ClO formations without water vapour, the effective rate constant of H2O???HO2 + HOCl reaction is estimated to be faster than the naked reaction by 2–3 orders of magnitude, indicating that the single water molecule in the H2O???HO2 + HOCl channel exhibits a positive catalytic effect on enhancing the rate of H2O2 + ClO formations. Meanwhile, it is interesting that the transfer process between H2O???HOCl + HO2 and H2O???HO2 + HOCl has an activation energy of 0.6 kcal?mol?1 and can occur easily under tropospheric conditions.  相似文献   

10.
ABSTRACT

Domain-based local pair natural orbital (DLPNO) coupled cluster single and double (CCSD) methods with perturbative triples (T) correction with NormalPNO were used to compute energies for twelve different S1 structures of the CaMn4O5 cluster in the oxygen evolving complex (OEC) of photosystem II (PSII). The DLPNO-CCSD(T0) calculations with TightPNO for the important six structures among them revealed that the right (R)-opened S1XYZW structures were more stable than the corresponding left (L)-opened structures (X?=?O(5), Y?=?W2, Z?=?W1, and W?=?O(4)) of CaMn4O5. The three different S1 structures belonging to the R-opened type (S1acca, S1bbca, and S1abcb, where O2-?=?a, OH-?=?b and H2O?=?c) were found nearly degenerated in energy, indicating the possibility of the coexistence of different structures in the S1 state. The DLPNO-CCSD(T0) calculations with TightPNO supported the proposal of a dynamic equilibrium model based on the multi-intermediate structures for the S1 state, which is also in agreement with EPR and other experimental and hybrid DFT computational results. Implications of the computational results are discussed in relation to scope and applicability of NormalPNO and TightPNO for the CCSD(T0) calculations of strongly correlated electron systems such as 3d transition-metal complexes.  相似文献   

11.
G2 ab initio molecular orbital calculations have been performed to study the potential energy surfaces (PESs) associated with the reactions of Cl+ in its 3P ground state and in its 1D first excited state with hydrogen sulphide. [H2, Cl, S]+ singlet and triplet state cations present very different bonding characteristics. The latter are systematically ion-dipole or hydrogen-bonded weakly bound species, while the former are covalent molecular ions. As a consequence, although the Cl+(3P) is 34.5 kcal mol?1 more stable than Cl+(1D), the global minimum of the singlet PES lies 37.3 kcal mol?1 below the global minimum of the triplet PES. Both singlet and triplet potential energy surfaces show significant differences with respect to those associated with Cl+ + H2O reactions as well as with SH2 reactions with F+. In both cases, the major product should be SH+ 2; SH+ and HCl+ being the minor products, in agreement with the experimental evidence. The estimated heat of formation for the most stable H2SCl+ singlet state species is 198 ± 1 kcal mol?1.  相似文献   

12.
Coupled-cluster singles and doubles (CCSD) valence shell correlation energies of the systems CH2 (<1A1 state), H2O, HF, N2, CO, Ne, and F2 are computed by means of standard calculations with correlation-consistent basis sets of the type cc-pVxZ (x = D, T, Q, 5, 6) and by means of explicitly correlated coupled-cluster calculations (CCSD-R12/B) with large uncontracted basis sets of the type 19s14p8d6f4g3h for C, N, O, F, and Ne and 9s6p4d3f for H. These CCSD-R12/B calculations provide reference values for the basis set limit of CCSD theory. The computed correlation energies are decomposed into singlet and triplet pair energies. It is established that the singlet pair energies converge as X?3 and the triplet pair energies as X?5 with the cardinal number of the correlation-consistent basis sets, and an extrapolation technique is proposed that takes into account their different convergence behaviour. Applied to the cc-pV5Z and cc-pV6Z results, this new extrapolation yields pair energies with a mean absolute deviation of 0.02 mEh from the CCSD-R12/B reference values. For the seven systems under study, the extrapolated total valence shell correlation energies agree to within 0.2 mEh with the CCSD-R12/B benchmark data.  相似文献   

13.
Zn/Zn5(OH)8Cl2·H2O flower-like nanostructures was electrodeposited on the coated Zn with poly (N-methyl pyrrole) in 0.1 M Zn (NO3)2 and 0.1 M KCl solution. The morphology and the structure of the Zn/Zn5(OH)8Cl2·H2O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728 cm−1 related to Zn5(OH)8Cl2·H2O. The FESEM results indicated that Zn/Zn5(OH)8Cl2·H2O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8 nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1 M KCl as supporting electrolyte was Zn5(OH)8Cl2·H2O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn5(OH)8Cl2·H2O flower-like nanostructure. The trapping of Cl and OH within pores can be considered as the reason for the formation of flowerlike Zn/Zn5(OH)8Cl2·H2O nanostructures in 0.1 M KCl.  相似文献   

14.
New lanthanide complexes with benzeneseleninic (ABSe) and 4-chloro-benzeneseleninic (ABSeCl) acids have been synthesized and characterized by elemental analysis, infrared and UV–visible spectroscopies. The emission spectra of the trivalent europium complexes presented the typical electronic 5D07FJ transitions of the ion (J=0–4). The ground-state geometries of the europium complexes have been calculated by using the Sparkle/AM1 model. From these results, the 4f–4f intensity parameters and energies of the ligand singlet and triplet excited states have been obtained. The lower emission quantum yield for the [Eu(ABSe)3(H2O)2](H2O)2 compound, as compared to the [Eu(ABSeCl)3(H2O)2] one, can be associated to the higher numbers of water molecules, in the first and second coordination spheres, that contribute to the luminescence quenching. The [Eu(ABSe)3(H2O)2](H2O)2 complex presents an intermediate state whose energy difference with respect to the first excited singlet state is resonant with three phonons from the water molecules, favouring a multiphonon relaxation process from the singlet state followed by a fast internal conversion process; this effect is less pronounced in the complex with the ABSeCl ligand. The luminescence decay curves of the gadolinium complexes indicate that the level responsible for the intramolecular energy transfer process has a triplet character for both compounds. The nephelauxetic effect in these compounds was investigated under the light of a recently proposed covalency scale based on the concept of overlap polarizability of the chemical bond.  相似文献   

15.
Jerzy Moc 《Molecular physics》2014,112(21):2781-2790
Al13H clusters have been considered candidates for cluster assembled materials. Here we have carried out benchmark calculations for the Al13H cluster, both neutral and anionic, with the aim of verifying the nature of stationary points on the potential energy surface, studying dynamics of H atom and determining an adiabatic electron affinity. A range of correlated methods applied include second-order perturbation theory (MP2), spin-component-scaled MP2, coupled electron pair (CEPA) and coupled cluster singles and doubles with perturbative triple corrections (CCSD(T)). These methods are used in combination with the correlation consistent basis sets through aug-cc-pVTZ including extrapolation to the complete basis set (CBS) limit. Performance of several different flavours of density functional theory (DFT) such as generalised gradient approximation (GGA), hybrid GGA, meta-GGA and hybrid-meta-GGA is assessed with respect to the ab initio correlated reference data. The harmonic force constant analysis is systematically performed with the MP2 and DFT methods. The MP2 results show that for neutral Al13H only the hollow structure is a potential energy minimum, with the bridged structure being a transition state for the H shift from the hollow site to the adjacent hollow site. The CCSD(T)/aug-cc-pVTZ (CCSD(T)/CBS) estimate of the energy barrier to this H shift is 2.6 (2.9) kcal/mol, implying that the H atom movement over the Al13H cluster surface is facile. By contrast, the DFT force constant analysis results suggest additional terminal and bridged minima structures. For the anion Al13H?, exhibiting ‘stiffer’ potential energy surface compared to the neutral, the existence of the hollow and terminal isomers is consistent with the earlier photoelectron spectroscopy assignment. The adiabatic electron affinity of Al13H is determined to be 2.00 and 1.95 eV (the latter including the ΔZPE correction) based on the CCSD(T) energies extrapolated to the CBS limit, whereas the respective CCSD(T)/CBS thermodynamic EA values are 2.79 and 2.80 eV.  相似文献   

16.
B. R. Mehta  V. N. Singh 《Pramana》2005,65(5):949-958
The central objective of this study is to investigate (i) size-dependent properties of In2O3 nanoparticles and (ii) the role of metal additives in enhancing the gas sensing response. For this purpose, In2O3 : Ag composite nanoparticle layers having welldefined individual nanoparticle size and composition have been grown by a two step synthesis method. Thermogravimetric analysis, X-ray diffraction and transmission electron microscopy have been used to study the effect of post-synthesis heat treatment on the size and structure of the nanoparticles. A first-time unambiguous observation of sizedependent lowering of transformation temperature has been explained in terms of lower cohesive energy of surface atoms and increase in surface-to-volume ratio with decrease in nanoparticle size. The gas sensing studies of In2O3 as well as the In2O3 : Ag composite nanoparticle layers have been studied as a function of size and composition. In2O3: Ag composite nanoparticle layers with 15% silver show a sensitivity of 436 and response time of 6 s for 1000 ppm of ethanol in air. Ag additives form a p-type Ag2O, which interact with n-type In2O3 to produce an electron-deficient space-charge layer. In the presence of ethanol, interfacial Ag2O reduces to Ag, creating an accumulation layer in In2O3 resulting in increased sensitivity  相似文献   

17.
The detailed reaction mechanism of 1-chloroethyl radical with NO2 is investigated theoretically. The results show that the title reaction is more favourable on the singlet potential energy surface than on the triplet one. For the singlet PES of CH3CHCl?+?NO2, it is shown that the CH3CHCl radical can react with NO2 to barrierlessly generate adduct a (H3CHClCNO2), b1 (H3CHClCONO-trans), and b2 (H3CHClCONO-cis), respectively. A total of six energetically reaction pathways and ten products are found. However, the most competitive path way is P1 (CH3CHO?+?ClNO), which can further dissociate to give P6 (CH3CHO?+?Cl?+?NO) and P2 (CH3CClO?+?HNO). The present results can lead to a deep understanding of the mechanism of the title reaction and may be helpful for understanding the halogenated ethyl chemistry.  相似文献   

18.
The possible mechanisms for proton transfer in ammonium aqueous solutions are discussed through ab initio LCAO-MO-SCF calculations for the following hydrogen-bonded complexes : [NH4 + … NH3] ; [NH4 + … OH2] ; [NH4 + … OH2 … OH2] ; [NH4 + … OH2 … NH3] and [H2O … NH4 + … OH2 … OH2]. The energy curve along the reaction coordinate is drawn for the first three systems. A double well potential curve is obtained for the two symmetrical systems with a very low barrier to proton transfer : 2·9 kcal/mole for the system [NH4 + … NH3] and 4·3 kcal/mole for the system [NH4 + … H2O … NH3]. For both systems the exchange mechanism involves three successive steps : association, transfer and dissociation. Solvation may affect the energetics of the first and third steps. For the unsymmetrical system NH4 + + H2O, the energy would increase continuously during the steps of proton transfer and dissociation. Hence the process of proton transfer between an ammonium ion and a water molecule may take place in solution only if assisted either by solvation or by a concerted push-pull mechanism involving a third molecule [NH4 + … OH2 … NH3]. Theoretical results for the systems [NH4 + … OH2 … OH2] and [NH3 … H3O+ … H2O] show, indeed, that solvation should make the proton transfer easier. In any case the proton transfer is found to occur through a contraction of the associated species formed in the first step.  相似文献   

19.
CCSD(T) and MP2 results using the aug-cc-pV5Z basis set are reported for chain, cyclic and other structures of the clusters (H2)n, n?=?2-8, (CO2)n, n?=?2-6 and (HF)n, n?=?2-8. In chain-like structures of (H2)n and (CO2)n, with the bonding type of the dimer maintained, the dissociation energy De of the dimer doubles for the trimer, triples for the tetramer, and so on. Due to these systems being dominated by short-range forces, interactions are essentially restricted to neighbouring monomers. For other types of (H2)n and (CO2)n structures, the multipliers relative to the dimerisation energy can be much higher. Dissociation energies for the hexamers in S6 symmetry of both H2 (379?cm?1) and CO2 (4925?cm?1) are over ten times the respective dimerisation energies. For the chain-like trimer of HF, however, De is in excess of double the dimer value. Mainly due to longer-range dipolar forces, the interactions reach beyond the neighbouring monomers. The interaction energy between HF monomers in chains follows an approximate R?2 (R being the F–F distance) relationship, The calculated dissociation energies of the HF octamer are 15,985?cm?1 (factor of 10.4) for the chain, and 21,003?cm?1 (factor of 13.7) for the C6h cyclic structure.  相似文献   

20.
刘玉芳  和小虎  施德恒  孙金锋 《中国物理 B》2011,20(7):78201-078201
Quasi-classical trajectory theory is used to study the reaction of O(3P) with H2 (D2) based on the ground 3A' potential energy surface (PES). The reaction cross section of the reaction O+H2 → OH+H is in excellent agreement with the previous result. Vector correlations, product rotational alignment parameters 〈P2 (j'·k)〉 and several polarized-dependent differential cross sections are further calculated for the reaction. The product polarization distribution exhibits different characteristics that can be ascribed to different motion paths on the PES, arising from various collision energies or mass factors.  相似文献   

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