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1.
Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the X(2)B2 state of ScO2 and the 1A1 state of ScO2(-) were computed, employing the augmented correlation-consistent polarized-weighted core-valence quadruple-zeta (aug-cc-pwCVQZ) basis set for Sc and augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set for O, and with the outer core Sc 3s(2)3p(6) electrons being explicitly correlated. Franck-Condon factors, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the first photodetachment band of ScO2(-). The simulated spectrum matches well with the corresponding experimental 355 nm photodetachment spectrum of Wu and Wang, J Phys Chem A 1998, 102, 9129, confirming the assignment of the photodetachment spectrum and the reliability of the RCCSD(T) PEFs used. Further calculations on low-lying electronic states of ScO2 gave adiabatic relative electronic energies (T(e)'s) of, and vertical excitation energies (T(v)'s) to, the 2A1, 2B1, and 2A2 states of ScO2 (from the X(2)B2 state of ScO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the 1A1 state of ScO2(-). 相似文献
2.
Maggie Ng Daniel K. W. Mok Edmond P. F. Lee John M. Dyke 《Journal of computational chemistry》2013,34(7):545-557
The minimum energy path (MEP) of the reaction, CF3CHFCF3 + H → transition state (TS) → CF3CFCF3 + H2, has been computed at different ab initio levels and with density functional theory (DFT) using different functionals. The computed B3LYP/6‐31++G**, BH&HLYP/cc‐pVDZ, BMK/6‐31++G**, M05/6‐31+G**, M05‐2X/6‐31+G**, UMP2/6‐31++G**, PUMP2/6‐31++G**//UMP2/6‐31++G**, RCCSD(T)/aug‐cc‐pVDZ//UMP2/6‐31++G**, RCCSD(T)/aug‐cc‐pVTZ(spd,sp)//UMP2//6‐31++G**, RCCSD(T)/CBS//M05/6‐31+G**, and RCCSD(T)/CBS//UMP2/6‐31++G** MEPs, and associated gradients and Hessians, were used in reaction rate coefficient calculations based on the transition state theory (TST). Reaction rate coefficients were computed between 300 and 1500 K at various levels of TST, which include conventional TST, canonical variational TST (CVT) and improved CVT (ICVT), and with different tunneling corrections, namely, Wigner, zero‐curvature, and small‐curvature (SCT). The computed rate coefficients obtained at different ab initio, DFT and TST levels are compared with experimental values available in the 1000–1200 K temperature range. Based on the rate coefficients computed at the ICVT/SCT level, the highest TST level used in this study, the BH&HLYP functional performs best among all the functionals used, while the RCCSD(T)/CBS//MP2/6‐31++G** level is the best among all the ab initio levels used. Comparing computed reaction rate coefficients obtained at different levels of theory shows that, the computed barrier height has the strongest effect on the computed reaction rate coefficients as expected. Variational effects on the computed rate coefficients are found to be negligibly small. Although tunneling effects are relatively small at high temperatures (~1500 K), SCT corrections are significant at low temperatures (~300 K), and both barrier heights and the magnitudes of the imaginary frequencies affect SCT corrections. © 2012 Wiley Periodicals, Inc. 相似文献
3.
Preparation and Spectroscopic Characterization of the Difluoroaminofluoro-iminium-hexafluorometallates F2NC(F)NX2+MF6– (X = H, D; M = As, Sb) Difluorocyanamin, F2NCN, does not react with the superacids XF/MF5 (X = H, D; M = As, Sb) under formation of protonated nitrilium salts. At –78 °C iminium salts of the general form F2NC(F)NX2+MF6– are observed, which are characterized by vibrational and nmr spectroscopy. The structure and vibrational frequencies were computed ab initio at the Hartree-Fock (HF/6-31 + G*) and correlated Møller-Plesset (MP2/6-31 + G*) levels of theory. 相似文献
4.
The N-methylformamide(NMF)-water clusters were studied by ab inito calculations at MP2/6-31+G** and MP2 / 6-311 ++ G(d,p)levels. The equilibrium geometries and the dissociation channels and dissociation energies of both neutral and ionic NMF-H2O clusters are presented. For N-methylformamide,cis-form has lower energy than trans-form. In NMFH+,the proton prefers to link with the O atom of N-methylformamide. The results show that both cis- and trans- form of NMF can form a linear hydrogen bond with water. Although the energy of trans-NMF is higher than cis-NMF,trans-form exits more stably because it can form a double hydrogen bond with water. After the ionization of the NMF-H2O cluster,both the cis- and the trans-form will produce protonated products. 相似文献
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Mechanism of Dissolution of a Lithium Salt in an Electrolytic Solvent in a Lithium Ion Secondary Battery: A Direct Ab Initio Molecular Dynamics (AIMD) Study
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Dr. Hiroto Tachikawa 《Chemphyschem》2014,15(8):1604-1610
The mechanism of dissolution of the Li+ ion in an electrolytic solvent is investigated by the direct ab initio molecular dynamics (AIMD) method. Lithium fluoroborate (Li+BF4?) and ethylene carbonate (EC) are examined as the origin of the Li+ ion and the solvent molecule, respectively. This salt is widely utilized as the electrolyte in the lithium ion secondary battery. The binding of EC to the Li+ moiety of the Li+BF4? salt is exothermic, and the binding energies at the CAM–B3LYP/6‐311++G(d,p) level for n=1, 2, 3, and 4, where n is the number of EC molecules binding to the Li+ ion, (EC)n(Li+BF4?), are calculated to be 91.5, 89.8, 87.2, and 84.0 kcal mol?1 (per EC molecule), respectively. The intermolecular distances between Li+ and the F atom of BF4? are elongated: 1.773 Å (n=0), 1.820 Å (n=1), 1.974 Å (n=2), 1.942 Å (n=3), and 4.156 Å (n=4). The atomic bond populations between Li+ and the F atom for n=0, 1, 2, 3, and 4 are 0.202, 0.186, 0.150, 0.038, and 0.0, respectively. These results indicate that the interaction of Li+ with BF4? becomes weaker as the number of EC molecules is increased. The direct AIMD calculation for n=4 shows that EC reacts spontaneously with (EC)3(Li+BF4?) and the Li+ ion is stripped from the salt. The following substitution reaction takes place: EC+(EC)3(Li+BF4?)→(EC)4Li+?(BF4?). The reaction mechanism is discussed on the basis of the theoretical results. 相似文献
7.
Dr. Sven Tobisch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8290-8300
A detailed computational exploration of mechanistic intricacies of the copper(I) hydride (CuH)‐catalysed hydroamination of styrene with a prototype hydroxylamine ester by a recently reported [(dppbz)CuH] catalyst (dppbz≡{P^P}≡1,2‐bis(diphenylphosphino)‐benzene) is presented. A variety of plausible mechanistic avenues have been pursued by means of a sophisticated computational methodology, from which a general understanding of the factors controlling hydroamination catalysis emerged. The catalytically competent {P^P}CuI hydride, which is predominantly present as its dimer, involves in irreversible hydrocupration proceeding with complete 2,1 regioselectivity to form a secondary {P^P}CuI benzyl intermediate. Its interception with benzylamine ester produces the branched tertiary amine product and {P^P}CuI benzoate upon intramolecular SN2 disruption of the amine electrophile′s N?O linkage, to precede a highly rapid, strongly exergonic C?N bond‐forming reductive elimination. The {P^P}CuI benzoate corresponds to the catalyst resting state and its conversion back into the {P^P}CuI hydride upon transmetalation with a hydrosilane is turnover limiting. The effect of electronic perturbations at the amine electrophile upon the reaction rate for productive hydroamination catalysis and also non‐productive reduction of the hydroxylamine ester has been gauged, which unveiled a more fundamental insight into catalytic structure‐performance relationships. 相似文献
8.
1,1,2,2,3,3,4‐Heptafluorocyclopentane (F7A) has considerable potential to be a new halon replacement due to its environmental friendliness and low‐toxicity. However, the reaction processes of F7A with hydroxyl and hydrogen free radicals, which are of great importance for investigating its fire suppression mechanisms, are still unclear. In this paper, ab inito and density functional theory are used to deduce the possible reaction pathways for the reactions of F7A with hydroxyl and hydrogen free radicals at the CCSD/cc‐pVDZ//B3LYP/6‐311++G (d,p) level of theory. Two distinct reaction pathways including ten elementary reaction channels for F7A with hydroxyl free radical, and five distinct reaction pathways including twenty elementary reaction channels for F7A with hydrogen free radical are investigated. The geometries, vibrational frequencies and reaction energy barriers are also determined. Based on the calculated results, the possible reaction mechanisms are proposed and discussed. The most feasible reaction channel for F7A with hydroxyl free radical is that leads to CH(OH)CH2(CF2)3+·F, and the most feasible reaction channel for F7A with hydrogen free radical is that leads to (CF2)3CH2CH·+HF. The study is helpful to further study its fire suppression mechanisms and promote it to be a new generation of halon replacement. 相似文献
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Quantum mechanical ab initio calculations at the MP2 and CCSD(T) level of theory have been used to investigate the geometries and bond energies of the complexes M(CO)6–x(H2)x (M = Cr, Mo, W; x = 1, 2, 3). The theoretically predicted M(CO)5–(H2) bond dissociation energies are in excellent agreement with experimental values. The M–(H2) dissociation energies of the bis- and tris-dihydrogen complexes are very similar to the values for the mono-dihydrogen complexes. In M(CO)5(H2) the dihydrogen ligand prefers an eclipsed conformation relative to the equatorial carbonyl groups. For M(CO)4(H2)2 the cis and trans isomers are nearly equal in energy for M = W, while a cis configuration is favoured for M = Cr. For M(CO)3(H2)3 the facial configurations are more stable than the meridial structures for all three metals M. The charge decomposition analysis (CDA) classifies dihydrogen as a donor ligand with moderate acceptor properties. In trans-M(CO)4(H2)2 back donation is increased and the M–(H2) bonds are stronger than in M(CO)5–(H2). Back donation in M(CO)3(H2)3 is slightly weaker than in the mono-dihydrogen complexes M(CO)5(H2). 相似文献
11.
Nobuyuki Akai Satoshi Kudoh Masao Takayanagi Munetaka Nakata 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):93-100
Rotational isomerization of 2-chlorobenzaldehyde in low-temperature rare-gas matrices has been investigated by vibrational and electronic spectroscopies with aids of the density functional theory (DFT) and configuration interaction single (CIS) calculations. Infrared spectrum of the less stable O-cis isomer, produced from the more stable O-trans isomer upon UV irradiation, is measured with an FT-IR spectrophotometer. The enthalpy difference between the O-cis and O-trans isomers is estimated to be 9.7±0.2 kJ mol−1 from the temperature dependence of the infrared band intensities. Analyses of the infrared and electronic absorption spectral changes after UV irradiation and the phosphorescence spectra measured at various excitation wavelengths suggest that the rotational isomerization occurs via the intersystem crossing from S1 to T1. 相似文献
12.
The gas phase chemical reaction, H? + H2O → H2 + OH, and the effect of an additional water molecule on the reaction, H?(H2O) + H2O → H2 + OH(H2O), have been investigated. The optimal structures and energies of the reactants, products, two stable intermediates, and the transition state connecting the two intermediates have been determined. The additional water molecule does not affect the potential surface congruently: it destabilizes the H(H2O) minimum, but stabilizes the H2 ?OH minimum and the transition state connecting the two intermediates. However, it stabilizes the products more than the H2 ?OH? minimum. Finally, in line with the reduction in the barrier height, the transition state for the H(H20) to H2 ?OH? isomerization moves further along the reaction path. 相似文献
13.
Marek J. Wjcik Marek Boczar Marzena Stoma 《International journal of quantum chemistry》1999,73(3):275-282
Theoretical simulation of the bandshape and fine structure of the νs stretching band is presented for tropolone‐H and tropolone‐D taking into account an adiabatic coupling between the high‐frequency O–H(D) stretching and the low‐frequency intra‐ and intermolecular OO stretching modes, and linear and quadratic distortions of the potential energies for the low‐frequency vibrations in the excited state of the O–H(D) stretching vibration. In order to determine the low‐frequency vibrations, the experimental spectra of the polycrystalline tropolone in the far‐infrared and the low‐frequency Raman range have been recorded for the first time. The experimental frequencies in the low‐frequency region are compared with the results of the HF/6‐31G** and Becke3LYP/6‐31G** calculations carried out for the tropolone dimer. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 275–282, 1999 相似文献
14.
The microwave spectra of (CH3)2PSF, (CH3)(CD3)PSF, (CD3)2PSF, and (CH3)2P34SF have been investigated from 20.0 to 40.0 GHz. Botha-type R branch andc-type Q branch transitions have been measured in the ground states of each isotopic species. From a least-square adjustment to fit 12 rotational constants, the following structural parameters were obtained:r(P–F)=1.582 ± 0.003 Å;r(P=S)=1.902 ± 0.001 Å;r(P-C)=1.800 ± 0.001 Å;r(C-H)=1.088 ± 0.002 Å; HCP=109.28 ± 0.12°; SPF=114.50 ± 0.13°; and SPC=116.33 ± 0.06°. From Stark effect measurements, the dipole moment components have been determined to be ¦
a
¦ =3.556 ± 0.005; ¦
c
¦=2.026 ± 0.009; and ¦
t
¦=4.093 ± 0.009 (D). The Raman spectra (3200 to 100 cm–1) of each isotopic species have been measured for the solid, and liquid and qualitative depolarization values obtained. Additionally, the mid-infrared spectra (3200 to 500 cm–1) of the solids have been recorded. Proposed assignments of the normal modes have been made on the basis of Raman depolarization values and group frequencies which are supported by normal coordinate analysis utilizing an ab initio force field. Optimized structural parameters have been obtained with both the 3-21G* and 6-31G* basis sets. These results are compared to the corresponding quantities for several similar molecules.For part XLVIII, seeJ. Raman Spectrosc.1922,23, 107. 相似文献
15.
The infrared spectra (3200-50 cm–1) of gaseous and solid vinyltrichlorosilane, CH2=CH-SiCl3, have been recorded. In addition, the Raman spectrum (3200-10 cm–1) of the liquid has been recorded and quantitative depolarization values obtained. The infrared spectrum of the sample dissolved in liquid xenon (–80°C) has also been recorded. Using the experimental data and normal coordinate calculations with scaled ab initio force constants, the complete vibrational assignment is proposed. The torsional mode was observed in the infrared spectrum of the gas at 69 cm–1 and the threefold barrier of internal rotation was calculated to be 500 cm–1 (5.98 kJ/mol). Ab initio calculations have been carried out at the restricted Hartree–Fock level of the theory as well as with full electron correlation by the perturbation method to second order with different basis sets up to 6-311+G(d,p) to obtain the optimized geometries, harmonic force constants, infrared intensities, Raman activities, depolarization ratios, and vibrational frequencies. The ab initio predicted structural parameters are compared with those obtained from a previous electron diffraction study. 相似文献
16.
Anton Gatial Štěpán Sklenák Viktor Milata Peter Klaeboe Stanislav Biskupič Dieter Scheller Jana Jurašková 《Structural chemistry》1996,7(1):17-36
The IR and Raman spectra of aminomethylene propanedinitrile (AM) [H2N-CH=C(CN)2], (methylamino)methylene propanedinitrile (MAM) [CH3NH-CH=C(CN)2] and (dimethylamino)methylene propanedinitrile (DMAM) [(CH3)2N-CH=C(CN)2] as solids and solutes in various solvents have been recorded in the region 4000-50 cm–1. AM and DMAM can exist only as one conformer. From the vibrational and NMR spectra of MAM in solutions, the existence of two conformers with the methyl group orientedanti andsyn toward the double C=C bond were confirmed. The enthalpy difference H
0 between the conformers was measured to be 3.7±1.4 kJ mol–1 from the IR spectra in acetonitrile solution and 3.4±1.1 kJ mol–1 from the NMR spectra in DMSO solution. Semiempirical (AM1, PM3, MNDO, MINDO3) and ab initio SCF calculations using a DZP basis set were carried out for all three compounds. The calculations support the existence of two conformersanti andsyn for MAM, withanti being 7.8 kJ mol–1 more stable thansyn from ab initio and 8.6, 13.4, 11.6, and 10.8 kJ mor–1 from AM1, PM3, MNDO, and MINDO3 calculations, respectively. Finally, complete assignments of the vibrational spectra for all three compounds were made with the aid of normal coordinate calculations employing scaled ab initio force constants. The same scale factors were optimized on the experimental frequencies of all three compounds, and a very good agreement between calculated and experimental frequencies was achieved. 相似文献
17.
Semiempirical (MINDO/3, AM1, PM3, MNDO) and ab initio (4-31G and 4-3IG + dAO/S basis sets) calculations on the relative stabilities and structures of the five potential tautomeric forms of rhodanine are reported. It is shown that all methods (excepting PM3) predict as most stable 2-thioxo-4-thiazolidinone. These results correspond to the known experimental data. The infrared spectrum of rhodanine was recorded for the region 4000-150 cm–1, and the characteristic bands were compared with AM1 and 4-31G + dAO/S calculated frequencies. The transition states between five pairs of all possible tautomeric forms of the rhodanine were found by the AM1 method. 相似文献
18.
James R. Durig Gamil A. Guirgis J. F. Sullivan T. J. Dickson D. T. Durig 《Structural chemistry》2001,12(2):149-170
The Raman (3500–40 cm–1) and infrared (3500–70 cm–1) spectra of gaseous and solid 2-methoxypropene, CH3O(CH3)C=CH2, and the isotopomers, CD3O(CH3)C=CH2 and CH3O(CD3)C=CD2 have been recorded. In addition, the Raman spectra of the liquids have been recorded with qualitative depolarization measurements. All of these data indicate that only one conformer is present in the fluid phases at ambient temperature and this form is the cis conformer, which remains in the solid. Assignments are provided for the fundamentals of all three isotopomers for the cis conformer with Cs symmetry. The far-infrared spectra of all three isotopic species have been recorded at a resolution of 0.1 cm–1 in the gas and 1.0 cm–1 in the solid. The parameters of the potential function governing the asymmetric torsion are determined to be V3 = 1485 ± 9 cm–1 and V6 = –55 ± 4 cm–1 for the d0 compound, where only two terms were determined, since a second conformer was not evident. The barrier to internal rotation for the methyl group attached to the oxygen atom is 1370 ± 8 cm–1 and the C—CH3 barrier is 772 ± 5 cm–1. Ab initio calculations with full electron correlation have been carried out by the perturbation method to second order to obtain the equilibrium structural parameters, harmonic force constants, fundamental frequencies, infrared intensities, Raman activities, depolarization values, and conformational stability. The predicted values have been compared to the experimental values where appropriate. 相似文献
19.
Ab initio calculations [MP2, MP4SDTQ, and QCISD(T)] using different basis sets [6-31G(d,p), cc-pVXZ (X = D, T, Q), and aug-cc-pVDZ] and density functional theory [B3LYP/6-31G(d,p)] calculations were carried out to study the OCS.(CO2)2 van der Waals trimer. The DFT has proved inappropriate to the study of this type of systems where the dispersion forces are expected to play a relevant role. Three minima isomers (two noncyclic and one cyclic) were located and characterized. The most stable isomer exhibits a noncyclic barrel-like structure whose bond lengths, angles, rotational constants, and dipole moment agree quite well with the corresponding experimental values of the only structure observed in recent microwave spectroscopic studies. The energetic proximity of the three isomers, with stabilization energies of 1442, 1371, and 1307 cm-1, respectively, at the CBS-MP2/cc-pVXZ (X = D, T, Q) level, strongly suggests that the two unobserved structures should also be detected as in the case of the (CO2)3 trimer where both noncyclic and cyclic isomers have been reported to exist. The many-body symmetry-adapted perturbation theory is employed to analyze the nature of the interactions leading to the formation of the different structures. The three-body contributions are small and stabilizing for the two most stable structures and almost negligible for the cyclic isomer. 相似文献
20.
Yordanka Dimitrova Bistra A. Stamboliyska 《International journal of quantum chemistry》2003,92(6):506-515
The vibrational characteristics (vibrational frequencies and infrared intensities) for free and complexed CO and HONO2 have been predicted using ab initio calculations at SCF and MP2 levels with different basis sets and B3LYP/6?31G(d,p) calculations. The ab initio calculations show that the complexation between HONO2 and CO leads to two stable structures: CO … HONO2 (1A) and OC … HONO2 (1B). The changes in the vibrational characteristics from free monomers to complexes have been estimated. It was established that the most sensitive to the complexation is the stretching O? H vibration. In agreement with the experiment, its vibrational frequency in the complexes is shifted to lower frequency (Δν = ?123 cm?1). The magnitude of the wave number shift is indicative of relatively strong hydrogen‐bonded interaction. The ab initio calculations at different levels predict an increase of the infrared intensity of the stretching O? H vibration for structure 1A more than five times and for structure 1B more than nine times. The most consistent agreement between the computed values of the frequency shifts for structure 1B and those experimentally observed suggests that this structure is preferred. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献