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1.
2.
Kouichi Takeshita 《Theoretical chemistry accounts》1999,101(5):343-351
Ab initio calculations have been performed to study the molecular structures and the vibrational levels of the first ionic
states of vinyl fluoride, vinyl chloride, trifluoroethylene, and trichloroethylene. The equilibrium molecular structures and
vibrational modes of these states are presented. The theoretical ionization intensity curves including the vibrational structures
are also presented and compared with the photoelectron spectra.
Received: 11 September 1998 / Accepted: 13 October 1998 / Published online: 1 February 1999 相似文献
3.
The three-dimensional (3D) potential energy surface of the ground state of Li3 was determined by the multireference configuration interaction method. The vibrational motions and pseudorotation were investigated
by a 3D time-dependent wavepacket formalism. The analytical expression of the 3D surface is given and the results of vibrational
analyses at several critical points are presented. The low-lying excited states of Li3 were examined for the C
2
v
structure and the vertical and adiabatic excitation energies were calculated. The ground and singlet excited states of Li2 were calculated and their spectroscopic constants compare well with the experimental values. A 3D wavepacket calculation
was performed for simulations of the stimulated emission pumping spectrum in which the A state was taken as an intermediate.
The recurrences of the autocorrelation functions were characterized by classical trajectory calculations. The autocorrelation
functions obtained by wavepacket propagation are reproduced well by the accumulation of the classical trajectories in the
short-time region.
Received: 2 July 1998 / Accepted: 3 September 1998 / Published online: 8 February 1999 相似文献
4.
The van der Waals pyrrole dimer is studied using supermolecular and perturbation ab initio treatment with inclusion of correlation
energy. The influence of selected geometry variations on the interaction energy components is investigated. Our calculations
verified the minimum on the potential energy surface deduced from microwave spectra. Its stability is possibly related not
to the extremal values of the selected interaction energy contributions but its physical origin is connected with the delicate
equilibrium between the repulsive and attractive forces. Any structure variation connected with the extremal attraction energy
is more than compensated for by the repulsion energy.
Received: 11 June 1998 / Accepted: 6 October 1998 / Published online: 1 February 1999 相似文献
5.
Using established methods based on correlated atomic natural orbitals (ANOs), sets of contracted polarization functions are
derived for use in calculations of atomic and molecular electrical properties (especially electric moments, dipole polarizabilities
and related property hypersurfaces). Through test calculations on Ne, Ar, NH3 and CO2, these polarization functions are shown to reproduce the accuracy of larger basis sets, to incorporate dynamical electron
correlation effects and are economical to use in conjunction with sophisticated electron-correlation treatments. We also show
how triple-zeta polarized ANO and double-zeta polarized ANO basis sets are constructed from these contracted polarization
functions for use in the calculation of reliable zero-point vibrational averages of electrical properties.
Received: 20 December 1999 / Accepted: 15 February 2000 / Published online: 12 May 2000 相似文献
6.
By the use of translation formulas for the expansion of Slater-type orbitals (STOs) in terms of STOs at a new origin, three-center
electric and magnetic multipole moment integrals are expressed in terms of two-center multipole moment integrals for the evaluation
of which closed analytical formulas are used. The convergence of the series is tested by calculating concrete cases. Computer
results with an accuracy of 10−7 are obtained for 2ν– pole electric and magnetic multipole moment integrals for 1≤ν≤5 and for arbitrary values of screening constants of atomic
orbitals and internuclear distances.
Received: 28 October 1999 / Accepted: 15 February 2000 / Published online: 5 June 2000 相似文献
7.
Cheol Ho Choi Miklos Kertesz Sergey Dobrin Josef Michl 《Theoretical chemistry accounts》1999,102(1-6):196-206
s-trans, s-cis and gauche conformers of 1,3-butadiene have been studied using density functional theory and the coupled-cluster
method using double substitutions (CCD). Matrix isolation Raman and IR data for the minor conformer were obtained and are
used in combination with the theoretical results to resolve earlier ambiguities in vibrational assignments. Based on high-quality
Hessians, new harmonic stretching force constants are reported for the carbon backbone of s-trans-1,3-butadiene. For the minor conformer the best unscaled root mean square error of the calculated frequencies for the s-cis
and gauche geometries are 17.5 cm−1 and 7.4 cm−1, respectively, primarily due to a better agreement of the gauche results for the vibrations at 983 cm−1, 596 cm−1 and 470 cm−1 which depend strongly on the torsional angle. Although this points towards the gauche form rather than the s-cis form, the
calculated transition dipole moment directions at the CCD/6-311G(d,p) level confirm the earlier conclusion that the minor
conformer has C
2
v
symmetry in the matrix. It is concluded that either the better agreement between the frequencies calculated for the gauche
form and the observed values is coincidental, or that the molecule is indeed nonplanar in the matrix and tunnels very rapidly
between the two mirror-image forms (or its lowest vibrational level lies above the barrier).
Received: 1 July 1998 / Accepted: 26 October 1998 / Published online: 15 February 1999 相似文献
8.
Using a systematic series of basis sets in supermolecular and symmetry-adapted intermolecular perturbation theory calculations
it is examined how interaction energies of various water dimer structures change upon addition and shifting of bond functions.
Their addition to augmented double- and triple-zeta basis sets brings the sum of the electron correlation contributions to
the second-order interaction energy nearly to convergence, while accurate first-order electrostatic and exchange contributions
require better than augmented quadruple-zeta quality. A scheme which combines the different perturbation energy contributions
as computed in different basis subsets performs uniformly well for the various dimer structures. It yields a symmetry-adapted
perturbation theory value of −21.08 kJ/mol for the energy of interaction of two vibrationally averaged water molecules compared
to −21.29 kJ/mol when the full augmented triple-zeta basis set is used throughout.
Received: 4 November 1999 / Accepted: 8 February 2000 / Published online: 12 May 2000 相似文献
9.
Maja Nendel Bernd Goldfuss K. N. Houk Klaus Hafner Udo Grieser 《Theoretical chemistry accounts》1999,102(1-6):397-400
B3LYP/6-31G* calculations on bis-periazulene (cyclohepta[def]-fluorene) predict a triplet ground state for this molecule. The singlet has an aromatic 14π-electron periphery but is 2 kcal/mol
higher in energy. The results agree with earlier predictions by Heilbronner.
Received: 19 August 1998 / Accepted: 6 October 1998 / Published online: 23 February 1999 相似文献
10.
Kazunari Naka Hirofumi Sato Akihiro Morita Fumio Hirata Shigeki Kato 《Theoretical chemistry accounts》1999,102(1-6):165-169
The free-energy profile for the Menshutkin-type reaction NH3 + CH3Cl → NH3CH3
+ + Cl− in aqueous solution is studied using the RISM-SCF method. The effect of electron correlation on the free-energy profile is
estimated by the RISM-MP2 method at the HF optimized geometries along the reaction coordinate. Solvation was found to have
a large influence on the vibrational frequencies at the reactant, transition state and product; these vibrational frequencies
are utilized to calculate the zero-point energy correction of the free-energy profile. The computed barrier height and reaction
exothermicity are in reasonable agreement with those of experiment and previous calculations. The change of solvation structure
along the reaction path is represented by radial distribution functions between solute-solvent atomic sites. The mechanisms
of the reaction are discussed from the view points of solute electronic and solvation structures.
Received: 26 June 1998/Accepted: 28 August 1998 / Published online: 2 November 1998 相似文献
11.
Density functional theory transition structures were located for three concerted [6 + 4] cycloaddition reactions involving
cis-hexatriene and butadiene, cyclopentadiene and cycloheptatriene, and cyclopentadiene and tropone. Geometries, energies, and
entropies were computed at the Becke3LYP/6-31G* level. The activation energy of the concerted [6 + 4] cycloaddition of hexatriene
and butadiene is 33.3 kcal/mol, about 8 kcal/mol above the activation energy of the butadiene plus ethylene [4 + 2] cycloaddition.
The endo concerted [6 + 4] transition state is 1.1 kcal/mol higher than the exo. The [6 + 4] reaction of cyclopentadiene and
cycloheptatriene has a barrier of 25.9 kcal/mol, while the cyclopentadiene–tropone barrier drops to 20.7 kcal/mol.
Received: 3 December 1998 / Accepted: 18 February 1999 / Published online: 7 June 1999 相似文献
12.
Potential-energy curves for the ground state and lower excited states of the Cd2 dimer have been calculated. They are obtained using a multireference doubles excitation configuration interaction procedure
and employing Slater basis sets, previously optimized at the self-consistent-field level for excited states of the Cd atom.
The spectroscopic constants and excitation energies for the bound states of Cd2 have been compared with experimental as well as other theoretical results. The ground state of Cd2 is essentially repulsive and presents a shallow van der Waals minimum. The computed adiabatic electronic transitions are
in good agreement with the experimental ones.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000 相似文献
13.
Charles W. Bauschlicher Jr 《Theoretical chemistry accounts》1999,103(2):141-145
Correlation-consistent basis sets are developed for the Ti atom. The polarization functions are optimized for the average
of the 3F and 5F states. One series of correlation-consistent basis sets is for 3d and 4s correlation, while the second series includes 3s and 3p correlation as well as 3d and 4s correlation. These basis sets are tested using the Ti 3F–5F separation and the dissociation energies of TiCl X4Φ, TiH X4Φ, and TiH+ X3Φ. The CCSD(T) complete basis set limit values are determined by extrapolation. The Douglas–Kroll approach is used to compute
the scalar relativistic effect. Spin-orbit effects are taken from experiment and/or are computed at the CASSCF level. The
Ti 3F–5F separation is in excellent agreement with experiment, while the TiCl, TiH, and TiH+ bond energies are in good agreement with experiment. Extrapolation with the valence basis set is consistent with other atoms,
while including 3s and 3p correlation appears to make extrapolation more difficult.
Received: 20 January 1999 / Accepted: 26 February 1999 / Published online: 7 June 1999 相似文献
14.
We report ab initio calculations of the indirect nuclear spin–spin coupling constants of PbH4 using a basis set which was specially optimized for correlated calculations of spin–spin coupling constants. All nonrelativistic
contributions and the most important part of the spin–orbit correction were evaluated at the level of the random phase approximation.
Electron correlation corrections to the coupling constants were calculated with the multiconfigurational linear-response method
using extended complete and restricted active space wavefunctions as well as with the second-order polarization propagator
approximation and the second-order polarization propagator approximation with coupled-cluster singles and doubles amplitudes.
The effects of nuclear motion were investigated by calculating the coupling constants as a function of the totally symmetric
stretching coordinate. We find that the Fermi contact term dominates the Pb‐H coupling, whereas for the H‐H coupling it is
not more important than the orbital paramagnetic and diamagnetic contributions. Correlation affects mainly the Fermi contact
term. Its contribution to the one-bond coupling constant is reduced by correlation, independent of the method used; however,
the different correlated methods give ambiguous results for the Fermi contact contribution to the H‐H couplings. The dependence
of both coupling constants on the Pb‐H bond length is dominated by the change in the Fermi contact term. The geometry dependence
is, however, overestimated in the random phase approximation.
Received: 16 November 1998 / Accepted: 30 March 1999 / Published online: 14 July 1999 相似文献
15.
H. J. Choi C. A. Kim J. H. Sung C. B. Kim W. Chun M. S. Jhon 《Colloid and polymer science》2000,278(7):701-705
Polymer-induced turbulent drag reduction in a rotating disk apparatus was investigated using nonionic poly(ethylene oxide)
(PEO) in a synthetic saline solution with novel application to ocean thermal energy conversion technology. A maximum total
(skin friction plus form) drag reduction of 30% was obtained with 50 wppm of PEO with molecular weight 5.0 × 106. The concentration dependence of the percentage drag reduction for the PEO/saline solution system is found to fit Virk's
empirical correlation, and a universal correlation for various molecular weights and Reynolds numbers is also presented. Furthermore,
hydrodynamic volume fraction was introduced to correlate drag reduction efficiency with molecular parameters in this PEO/saline
solution system.
Received: 28 December 1999/Accepted: 17 February 2000 相似文献
16.
Hisayoshi Kobayashi Katsumi Nakashiro Tomoatsu Iwakuwa 《Theoretical chemistry accounts》1999,102(1-6):237-243
The mechanism of ethylene epoxidation on Ag surfaces has been investigated using the density functional method and Ag
n
clusters (n = 3 to 10) modeling the Ag(111) surface. The adsorption energy of O2 to the Ag clusters was strongly dependent on the HOMO level of the cluster, and the clusters with higher HOMO levels afforded
larger O2 adsorption energies. The energetics was investigated for both the molecular and atomic oxygen epoxidation mechanisms. For
the atomic oxygen mechanism, epoxidation was found to proceed without an activation energy, whereas a small amount of activation
energy (about 5 kcal/mol) was calculated for the molecular oxygen mechanism.
Received: 2 July 1998 / Accepted: 9 September 1998 / Published online: 8 February 1999 相似文献
17.
An adiabatic integration formula for the quantum chemistry correlation energy functional of the Hartree–Fock density, E
c
QC[n], is presented. The functional E
c
QC[n] is meant to be added to the completed Hartree–Fock energy to produce the exact ground-state energy of the system under consideration.
The initial slope of the integrand in this connection formula is identified as a second-order energy and an explicit expression
for the initial slope of the integrand is presented. Our expression should be useful for arriving at new improved approximations
to E
c
QC[n]. Previous numerical results by Huang and Umrigar (1997) Phys Rev A 56:290, for two-electron densities are proved, and a generalization to more than two electrons is presented. Results obtained
by means of the present density functional theory correlation energy functionals, when used to approximate the initial slope
in our adiabatic integration formula for E
c
QC[n], are compared against exact numbers.
Received: 10 September 1998 / Accepted: 3 February 1999 / Published online: 21 June 1999 相似文献
18.
J. F. Ogilvie S.-L. Cheah Y.-P. Lee S. P. A. Sauer 《Theoretical chemistry accounts》2002,108(2):85-97
From quantum-chemical calculations of rotational g factor and new experimental measurements of strengths of lines in infrared spectra of vibration–rotational bands v′–0 in absorption, with 1≤v′≤4, of 12C16O, and from analysis of 16,947 frequencies and wave numbers assigned to pure rotational and vibration–rotational transitions
within electronic ground state X
1Σ+, including new measurements of band 4–0 of 12C16O, we evaluate radial functions for potential energy and electric dipolar moment, the latter both in polynomial form and as
a rational function that has qualitatively correct behaviour under limiting conditions.
Received: 8 November 2001 / Accepted: 5 February 2002 / Published online: 14 August 2002 相似文献
19.
H. Strømsnes S. Jusuf A. Bagatur'yants O. Gropen U. Wahlgren 《Theoretical chemistry accounts》2001,106(5):329-338
The convergence of chemisorption energy for hydrogen and oxygen on gold clusters is studied. Two theoretical approaches have
been employed; wavefunction methods at the self-consistent-field second–order M?ller–Plesset level and density functional
theory and the two methods are compared. Relativistic effective core potentials exploited in the former approach were developed
in this work.
Received: 25 October 1999 / Accepted: 21 February 2001 / Published online: 11 October 2001 相似文献
20.
A quasi-classical trajectory (QCT) calculation with the fourth-order explicit symplectic algorithm for the N(4S) + O2(X3Σg−) → NO(X2Π) + O(3P) reaction has been performed by employing the ground and first-excited potential energy surfaces (PESs). Since the translational
temperature considered is up to 5000 K, the larger relative translational energy and the higher vibrational and rotational
level of O2 molecule have been taken into account. The affect of the relative translational energy, the vibrational and rotational level
of O2 molecule in the reaction cross-sections of the ground and first-excited PESs has been discussed in a extensive range. And
we exhibit the dependence of microscopic rate constants on the vibrational and rotational level of O2 molecule at T = 4000 K. The thermal rate constants at the translational temperature betweem 300 and 5000 K have been evaluated and the
corresponding Arrhenius curve has been fitted for reaction (1). It is found by comparison that the thermal rate constants
determined in this work have a better agreement with the experimental data and provide a more valid theoretical reference. 相似文献