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1.
Ping Qian Wei Song Linan Lu Zhongzhi Yang 《International journal of quantum chemistry》2010,110(10):1923-1937
Various properties of typical structures of water clusters in the n = 2–34 size regime with the change of cluster size have been systematically explored. Full optimizations are carried out for the structures presented in this article at the Hartree–Fock (HF) level using the 6‐31G(d) basis set by taking into account the positions of all atoms within the cluster. The influence of the HF level on the results has been reflected by the comparison between the binding energies of (H2O)n (n = 2–6, 8, 11, 13, 20) calculated at the HF level and those obtained from high‐level ab initio calculations at the second‐order Møller–Plesset (MP2) perturbation theory and the coupled cluster method including singles and doubles with perturbative triples (CCSD(T)) levels. HF is inaccurate when compared with MP2 and CCSD(T), but it is more practical and allows us to study larger systems. The computed properties characterizing water clusters (H2O)n (n = 2–34) include optimal structures, structural parameters, binding energies, hydrogen bonds, charge distributions, dipole moments, and so on. When the cluster size increases, trends of the above various properties have been presented to provide important reference for understanding and describing the nature of the hydrogen bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
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Anne-Marie Sapse Louis Osorio Grace Snyder 《International journal of quantum chemistry》1984,26(2):223-230
Ab initio calculations are performed with 6–31G basis set to study the geometry and binding of the H3O, H5O, H7O, and H9O complexes. The H3O complex is also investigated with the 6–31 G* basis set and MP 2 (Moller–Plesset perturbation theory of second order). 相似文献
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Ab initio theoretical calculations have been performed to study the reaction of O(2) with Ba(n) (n=2,5) clusters. Our results show that O(2) can easily chemisorb and dissociate on small Ba(n) clusters and there is no obvious energy barrier in the process of the dissociation. The local magnetic moment contributed by oxygen must vanish during the intermediate states before the O(2) dissociation. Correspondingly, local magnetic moment only decreases from 2 mu(B) to about 1 mu(B) if O(2) molecularly adsorbs onto Ba(5) cluster. The electronic structure analysis indicates that the charge transfer from Ba(n) cluster to O(2) as well as the orbital hybridization between the cluster and the oxygen molecule may play a key role in O(2) dissociation. 相似文献
5.
Anne-Marie Sapse Louis Osorio Grace Snyder 《International journal of quantum chemistry》1984,26(2):231-236
Clusters formed by the OH? ion and carbon dioxide are investigated using ab initio Hartree–Fock calculations, with 6–31 G and 6–31 G* basis sets. Geometries and binding energies are determined. 相似文献
6.
Larry A. Curtiss Carlos A. Melendres Alan E. Reed Frank Weinhold 《Journal of computational chemistry》1986,7(3):294-305
The interaction of superoxide ion O2? with up to four water molecules [O2?: (H2O)n, n = 1, 2, 4] has been investigated using ab initio molecular orbital theory. The binding energy of O2?: H2O is calculated to be ?20.6 kcal/mol in good agreement with gas phase experimental data. At the MP3/6-31G* level the O2?:H2O complex has a C2v structure with a double (cyclic) hydrogen bond between O2? and H2O. A Cs structure with a single hydrogen bond is only 0.7 kcal/mol less stable. Interaction of H2O with the doubly occupied π* orbital of O2? is preferred slightly over interaction with the singly occupied π* orbital. Natural bond orbital analysis suggests that both electrostatic and charge transfer interactions are important in anionic complexes. The charge transfer occurs predominantly in the O2? → H2O direction and is important in determining the relative stabilities of the different structures and states. Singly and doubly hydrogen-bonded structures for the O2?: (H2O)2 and O2?: (H2O)4 clusters were found to be similar in stability and the increase in binding of the cluster becomes smaller as each additional water molecule is added to the cluster. 相似文献
7.
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic ionization potentials of several water clusters: dimer, trimer, tetramer, pentamer, hexamer book, hexamer ring, hexamer cage, and hexamer prism. The present results establish reference values at a level not reported before for these systems, calibrating different computational strategies and helping to discard less reliable theoretical and experimental data. The systematic study with the increasing size of the water cluster allows obtaining some clues on the structure and reductive properties of liquid water. 相似文献
8.
The purpose of this article was to calculate the structures and energetics of CH3O−(H2O)n and CH3S−(H2O)n in the gas phase; the maximum number of water molecules that can directly interact with the O of CH3O−; and when n is larger, we asked how the CH3O− and CH3S− moiety of CH3O−(H2O)n and CH3S−(H2O)n changes and how we can reproduce experimental ΔH 0n−1, n. Using the ab initio closed-shell self-consistent field method with the energy gradient technique, we carried out full geometry optimizations with the MP2/aug-cc-pVDZ for CH3O−(H2O)n (n=0, 1, 2, 3) and the MP2/6–31+G(d,p) (for n=5, 6). The structures of CH3S−(H2O)n (n=0, 1, 2, 3) were fully optimized using MP2/6–31++G(2d,2p). It is predicted that the CH3O−(H2O)6 does not exist. We also performed vibrational analysis for all clusters [except CH3O−(H2O)6] at the optimized structures to confirm that all vibrational frequencies are real. Those clusters have all real vibrational frequencies and correspond to equilibrium structures. The results show that the above maximum number of water molecules for CH3O− is five in the gas phase. For CH3O−(H2O)n, when n becomes larger, the C—O bond length becomes longer, the C—H bond lengths become smaller, the HCO bond angles become smaller, the charge on the hydrogen of CH3 becomes more positive, and these values of CH3O−(H2O)n approach the corresponding values of CH3OH with the n increment. The C—O bond length of CH3O−(H2O)3 is longer than the C—O bond length of CH3O− in the gas phase by 0.044 Å at the MP2/aug-cc-pVDZ level of theory. The structure of the CH3S− moiety in CH3S−(H2O)n does not change with the n increment. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1138–1144, 1999 相似文献
9.
Study of Cl−(H2O)n (n = 1–4) using basin‐hopping method coupled with density functional theory
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Shuai Jiang Yi‐Rong Liu Teng Huang Hui Wen Kang‐Ming Xu Wei‐Xiong Zhao Wei‐Jun Zhang Wei Huang 《Journal of computational chemistry》2014,35(2):159-165
Cl?(H2O)n (n = 1–4) clusters were investigated using a basin‐hopping (BH) algorithm coupled with density functional theory (DFT). Structures, energetics, thermodynamics, vertical detachment energies, and vibrational frequencies were obtained from high‐level ab initio calculations. Through comparisons with previous theoretical and experimental data, it was demonstrated that the combination of the BH method and DFT could accurately predict the global and local minima of Cl?(H2O)n (n = 1–4). Additionally, to optimize larger Cl?(H2O)n (n > 4) clusters, several popular density functionals as well as DF‐LMP2 (Schütz et al., J. Chem. Phys. 2004, 121, 737) (second‐order Møller‐Plesset perturbation theory using local and density fitting approximations) were tested with appropriate basis sets through comparisons with MP2 optimized results. DF‐LMP2 will be used in future studies because its overall performance in describing the relative binding energies and the geometrical parameters of Cl?(H2O)n (n = 1–4) was outstanding in this study. © 2013 Wiley Periodicals, Inc. 相似文献
10.
Hydrogen-bonded heteroclusters of H(2)O(2)...(H(2)O)(n)(), with n varying from 1 through 6, have been investigated herein employing ab initio quantum chemical methods. For a given n, several energetically comparable conformers emerge as local minima on the potential energy surface (PES). All of the conformers obtained at restricted Hartree-Fock (RHF) and M?ller-Plesset second-order perturbation (MP2) levels of theory exhibit parallel trends in energy hierarchy. The effect of clustering by water on the modification in the vibrational frequencies has also been investigated and further, a many-body interaction-energy analysis is carried out providing insights into cooperativity in H(2)O(2)...(H(2)O)(n)() clusters. 相似文献
11.
Cabanillas-Vidosa I Rossa M Pino GA Ferrero JC Cobos CJ 《Physical chemistry chemical physics : PCCP》2012,14(12):4276-4286
An experimental and theoretical study of the photoionization energies (IE's) of Ba(H(2)O)(n) clusters containing up to n = 4 water molecules has been performed. The clusters were generated by a pick-up source combining laser vaporization with pulsed supersonic expansion, and then photoionized by radiation of 272.5-340 nm. The experimentally determined IE(e)'s for n = 1 to 4 are 4.56 ± 0.05, 4.26 ± 0.05, 3.90 ± 0.05 and 3.71 ± 0.05 eV. This cluster size dependence of IE is reproduced within ±0.06 eV employing the mPW1PW91 density-functional and CCSD(T, Full) quantum-chemical methods combined with the 6-311++G(d,p) basis set for the H and O atoms and three different relativistic effective core potentials for Ba atoms. The calculations indicate that the lowest energy hydration structures represent the most relevant contributions to both the vertical and adiabatic ionization energies. Experimental and theoretical evidence correlates with the progressive surface-delocalization of the electron from the hydration cavity around the Ba atom and suggests that the intra-cluster electron transfer is possible even for small aggregates. 相似文献
12.
Chaban GM Gerber RB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(4):887-898
Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the M?ller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments. 相似文献
13.
Ab initio molecular orbital theory is applied to the study of P? O and P? S bonding in the hypervalent phosphinic (H2POOH), phosphinothioic (H2POSH), and phosphinodithioic (H2PSSH) acid molecules. Intramolecular proton exchange reactions are followed using the intrinsic reaction coordinate and Self-Consistent-Field energy localized orbitals. The P? O and PS bonds are characterized via force constants, phosphorus d orbital populations, and localized orbitals and are best described as either normal single bonds or dative bonds augmented by π back donation from the oxygen or sulfur lone pairs. The anions of these acids are also investigated, and they are found to contain only dative bonds to sulfur and oxygen. 相似文献
14.
Neelamraju S Schön JC Doll K Jansen M 《Physical chemistry chemical physics : PCCP》2012,14(3):1223-1234
We explore the energy landscape of (MgF(2))(3) on both the empirical and ab initio level using the threshold algorithm. In order to determine the energy landscape and the dynamics of the trimer we investigate not only the stable isomers but also the barriers separating these isomers. Furthermore, we study the probability flows in order to estimate the stability of all the isomers found. We find that there is reasonable qualitative agreement between the ab initio and empirical potential, and important features such as sub-basins and energetic barriers follow similar trends. However, we observe that the energies are systematically different for the less compact clusters, when comparing empirical and ab initio energies. Since the underlying motivation of this work is to identify the possible clusters present in the gas phase during a low-temperature atom beam deposition synthesis of MgF(2), we employ the same procedure to additionally investigate the energy landscape of the tetramer. For this case, however, we use only the empirical potential. 相似文献
15.
Siu CK Fox-Beyer BS Beyer MK Bondybey VE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(24):6382-6392
An ab initio molecular dynamics method was used to compare the ionic dissolution of soluble sodium chloride (NaCl) in water clusters with the highly insoluble silver chloride (AgCl). The investigations focused on the solvation structures, dynamics, and energetics of the contact ion pair (CIP) and of the solvent-separated ion pair (SSIP) in NaCl(H(2)O)(n) and AgCl(H(2)O)(n) with cluster sizes of n = 6, 10 and 14. We found that the minimum cluster size required to stabilize the SSIP configuration in NaCl(H(2)O)(n) is temperature-dependent. For n = 6, both configurations are present as two distinct local minima on the free-energy profile at 100 K, whereas SSIP is unstable at 300 K. Both configurations, separated by a low barrier (<10 kJ mol(-1)), are identifiable on the free energy profiles of NaCl(H(2)O)(n) for n = 10 and 14 at 300 K, with the Na(+)/Cl(-) pairs being internally solvated in the water cluster and the SSIP configuration being slightly higher in energy (<5 kJ mol(-1)). In agreement with the low bulk solubility of AgCl, no SSIP minimum is observed on the free-energy profiles of finite AgCl(H(2)O)(n) clusters. The AgCl interaction is more covalent in nature, and is less affected by the water solvent. Unlike NaCl, AgCl is mainly solvated on the surface in finite water clusters, and ionic dissolution requires a significant reorganization of the solvent structure. 相似文献
16.
We have studied the protonated ether-(H2O)n (n = 1-3) complexes containing tetrahydrofuran, dimethyl, diethyl, dibutyl, and butylmethyl ethers using a flowing afterglow triple-quadrupole mass spectrometer. Collision-induced dissociation, CID, of all clusters with n = 1, 2 shows sequential water loss. The n = 3 cluster of dimethyl ether shows sequential water loss, while all other ether clusters display selective product formation. The CID spectra are interpreted based on known energetics, and theoretical studies of the dimethyl and diethyl ether systems. 相似文献
17.
Wei-Xing Xu K. D. Schierbaum W. Goepel 《International journal of quantum chemistry》1997,62(4):427-436
Electronic structures of a series of Ptn clusters (n = 2–12) have been calculated by ab initio method (SCF/MP2). The result shows that compared to that at the saturated coordination site, Pt at the unsaturated coordination site has lower Pt65 electron occupancies, and the relationship between the electronic structure and the cluster size has been discussed. It is found that when the number of Pt in cluster reaches 7, electronic structures become more like the metallic ones. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62 : 427–436, 1997 相似文献
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Xiu‐Li Dong Zheng‐Yu Zhou Lai‐Jin Tian Gang Zhao 《International journal of quantum chemistry》2005,102(4):461-469
The hydrogen bonding complexes HO(H2O)n (n = 1–3) were completely investigated in the present study using DFT and MP2 methods at varied basis set levels from 6‐31++G(d,p) to 6‐311++G(2d,2p). For n = 1 two, for n = 2 two, and for n = 3 five reasonable geometries are considered. The optimized geometric parameters and interaction energies for various complexes at different levels are estimated. The infrared spectrum frequencies and IR intensities of the most stable structures are reported. Finally, thermochemistry studies are also carried out. The results indicate that the formation and the number of hydrogen bonding have played an important role in the structures and relative stabilities of different complexes. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
20.
Marek J. Wjcik Gilbert J. Mains J. Paul Devlin 《International journal of quantum chemistry》1995,53(1):49-56
The geometries, successive binding energies, vibrational frequencies, and infrared intensities are calculated for the [Li(H2O)n]+ and [K(H2O)n]+ (n = 1?4) complexes. The basis sets used are 6-31G* and LANL 1DZ (Los Alamos ECP +DZ ) at the SCF and MP 2 levels. There is an agreement for calculated structures and frequencies between the MP 2/6-31G* and MP 2/LANL 1DZ basis sets, which indicates that the latter can be used for calculations of water complexes with heavier ions. Our results are in a reasonable agreement with available experimental data and facilitate experimental study of these complexes. © 1995 John Wiley & Sons, Inc. 相似文献