摘要:

A new global, ground-state, Born-Oppenheimer surface is presented for the H+3system. The energy switching approach has been used to combine different functional forms for three different regimes: a spectroscopic expansion at low energy, a Sorbie-Murrell function at high energy and known long-range terms combined with accurate diatomic potentials at large separations. At low energies we have used the ultra high accuracyab initiodata of Cenceket al.(1998,J. chem. Phys.,108, 2831). At intermediate energy we have calculated 134 newab initioenergies using a high accuracy, explicitly correlated procedure. Theab initiodata of Schinkeet al.(1980,J. chem. Phys.,72, 3909) has been used to constrain the high energy region. Two fits are presented which differ somewhat in their behaviour at energies over 45 000 cm−1above the H+3minimum. Below this energy, the fits reproduce each set ofab initiodata close to their intrinsic accuracy. The ground state surface should provide a suitable starting point for renewed studies of the near-threshold photodissociation spectrum originally reported by Carringtonet al.(1982,Molec. Phys.,45, 753).

ISSN:0026-8976    

DOI:10.1080/00268970009483290

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The conventional formulation of the dispersion energy as a power series inR−1with damping at smallRis re-examined. Symmetry-adapted and intermolecular perturbation theory calculations have been performed and compared for the argon dimer. We show that conventional Tang-Toennies damping functions fit the data better when exchange as well as charge-overlap effects are included. We also construct a new representation of the dispersion energy which provides a more accurate, but still quite compact, description of the dispersion energy, and suggest several simpler forms which would be suitable for describing dispersion more accurately in larger systems. Some preliminary results for the HF dimer are also described.

ISSN:0026-8976    

DOI:10.1080/00268970009483291

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The importance of aqueous mixtures as solvents has motivated the investigation of the usefulness of classical molecular dynamics simulation, using simple effective pair potentials and the Lorentz-Berthelot combining rules, to predict mixture viscosities and dielectric constants. In the acetonitrile-water system, near quantitative agreement with experiment is found; however, the calculated shear viscosity in the 2-propanol-water system is underpredicted by more than a factor of two. Moreover, the results do not appear to be strongly dependent on the mixture combining rules, as a 10% decrease in the unlike OO Lennard-Jones size parameter for this system had no discernable effect on the calculated viscosity. In both systems, the dielectric constant predictions were in qualitative accord with experiment, although systematically underpredicted as in the pure component models.

ISSN:0026-8976    

DOI:10.1080/00268970009483292

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Relative equilibria of molecules are classical trajectories corresponding to steady rotations about stationary axes during which the shape of the molecule does not change. They can be used to explain and predict features of quantum spectra at high values of the total angular momentumJin much the same way that absolute equilibria are used at lowJ.This paper gives a classification of the symmetry types of relative equilibria of AB2molecules and computes the relative equilibria bifurcation diagrams and normal mode frequencies for D2H+and H2D+. These are then fed into a harmonic quantization procedure to produce a number of predictions concerning the structures of energy level clusters and their rearrangements asJincreases. In particular the formation of doublet pairs is predicted for H2D+fromJ≈ 26.

ISSN:0026-8976    

DOI:10.1080/00268970009483293

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A new molecular dynamics algorithm is presented for integrating the equations of motion for a system of particles interacting with mixed continuous-impulsive forces. This method, which has been called collision Verlet, is constructed using operator splitting techniques similar to those that have been used successfully to generate a variety of molecular dynamics integrators. In numerical experiments, the collision Verlet method is shown to be superior to previous methods with respect to stability and energy conservation in long simulations.

ISSN:0026-8976    

DOI:10.1080/00268970009483294

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The exact vibration-rotation quantum mechanical kinetic energy operator (KEO) for centrally-connected penta-atomic molecules such as methane and its isotopomers is derived for two sets of internal valence coordinates: the polyspherical coordinates and the bond-angle valence coordinates. The vibrational KEO including the pseudo-potential term is discussed for two forms of the modified Jacobian. For the rotational and vibration-rotation coupling KEO, results for two schemes of embedding the body-fixed coordinate system are presented: the bond embedding and the bisector embedding. Full expressions for the bisector embedding are too complicated to give in detail, but the working connection between the two embedding schemes is given. The future applications, including the perturbative and variational calculation of the vibrations and/or rotations for centrally connected penta-atomic molecules using the vibration-rotation KEO expressions derived in this work, are discussed.

ISSN:0026-8976    

DOI:10.1080/00268970009483295

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

(Molecular Physics, 1998,93, 95–106)

ISSN:0026-8976    

DOI:10.1080/00268970009483296

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor