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  • 1
    Electronic Resource
    Electronic Resource
    Gaussian functions in Hylleraas-configuration interaction calculations: Potential curves for the e 3∑+u and the f 3∑+u states of hydrogen (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4941-4947 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The explicitly correlated wave function method (Hylleraas-CI) with Cartesian Gaussian basis sets has been used to calculate the potential curve for the e3∑+u and f 3∑+u states of the H2 molecule. Potential barriers of 215 and 10 300 cm−1 are predicted to exist in the e3∑+u and f 3∑+u states, respectively, and their nature analyzed. Spectroscopic constants for H2 and D2 derived from the curves are compared with experiments and other theoretical calculations. It is concluded that the present potential curves are the best theoretical ones to-date and their accuracy is probably as good as the scanty experimental data. No o3∑+u state below the f 3∑+u state is found in our calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457711
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of water from 10 to 1273 K (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5157-5165 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The molecular dynamics of liquid water have been simulated over a wide range of thermodynamic conditions using a five by five site–site model for the intermolecular potential recently developed by Evans. The model reproduces the pressure satisfactorily for temperatures up to 1273 K at constant density of 1 g/cm3. Within the uncertainty, the experimental pressure is also reproduced satisfactorily at the critical point. Two simulations at 773 and 1043 K have also been carried out at constant molar volume of 8.5 cm3/mol. The molecular dynamics of the sample were investigated at each state point with a range of auto- and cross-correlation functions. Some of these have been computed at constant molar volume over a 15 kbar range of pressure and 1000 K range of temperature. They suggest that diffusional dynamics in liquid water are largely determined by density. Some results at 10 (1 bar) and 77 K (1 bar) were obtained by "splat quenching'' at constant molar volume. The oxygen–oxygen pair distribution functions from these simulations have been compared with the results available from amorphous solid water at these temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454670
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of direct laboratory frame cross correlations in spherical, plate-like, and rod-like molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2685-2691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Direct laboratory frame cross correlation functions (ccfs) are reported for the spherical top sulfur hexafluoride, and the symmetric tops, methyl hexa-tri-yne, hexafluorobenzene, and benzene. The direct correlations appear between the molecular dipole moment and the molecular center-of-mass velocity. The simulation provides the time dependence of the correlation functions for all four molecules. A simple theory for the computer simulation results is given, based on linked Langevin equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453997
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  • 4
    Electronic Resource
    Electronic Resource
    Gaussian functions in Hylleraas-configuration interaction calculations. V. An accurate ab initio H+3 potential-energy surface (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4948-4955 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The near-equilibrium potential-energy surface of the 1A'1 ground state of H+3 has been calculated at 69 different points with the Hylleraas-configuration interaction method using 13s3p1d Cartesian Gaussian basis functions. This new surface is found to be substantially lower in absolute energy than all previous surface calculations. The equilibrium energy of the H+3 molecule has also been calculated with a larger 13s5p3d basis set. The minimum energy was found to be E=−1.343 827 9 hartrees at an internuclear distance of R=1.6500 bohrs in the equilateral triangle configuration. This energy is significantly (〉70 cm−1) lower than the previous best published variational calculation and is outside and below the error bars of the latest quantum Monte Carlo calculation. In addition, a medium-sized basis set of 13s4p2d orbitals was used to predict that the equilibrium separation is R=1.6499 bohrs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457712
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  • 5
    Electronic Resource
    Electronic Resource
    Gaussian functions in Hylleraas-configuration interaction calculations. III. Wave functions for the X 1ξ+g state of hydrogen (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2369-2372 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Hylleraas-CI method with Cartesian Gaussian basis functions of various sizes has been used to calculate the ground state energies and wave functions for the hydrogen molecule at internuclear distances of 1.0, 1.4011, 4.0, and 8.0 bohr. The best basis sets reproduce energies obtained with the confocal elliptical coordinates by Kolos et al. to within 0.3 cm−1. A few cross sections of the wave functions are presented graphically, showing clearly that the improvement of Hylleraas-CI over conventional CI is due to the presence of a slightly deeper Coulomb hole around the electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457046
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular dynamics of liquid water in a circularly polarized external field (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6040-6045 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dipole moment of the water molecule has been subjected to an external circularly polarized field of force and the effect on the molecular dynamics evaluated through novel laboratory and moving frame cross correlation functions (ccf 's) using molecular dynamics computer simulation. The field symmetry is such as to make possible the existence in both frames off diagonal elements of the ccf 's which disappear at field off equilibrium. The laboratory frame ccf 's involve simultaneously the rotational and translational motion of the molecule and are not describable with contemporary theories of "rotational'' or "translational'' diffusion. The simulation shows laboratory frame birefringence in the orientational and rotational velocity autocorrelation functions (acf 's) in the y (or z) and x axes for a field applied in the x axis. This birefringence is linked to the appearance of ccf elements induced by the circularly polarized field, and its experimental measurement would provide indirect information on the time dependence of these ccf 's.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453476
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  • 7
    Electronic Resource
    Electronic Resource
    Gaussian functions in Hylleraas-configuration interaction calculations. II. Potential curves for the b 3Σ+u and the e 3Σ+u states of hydrogen (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2366-2368 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Hylleraas-CI method with Cartesian Gaussian basis functions has been used to calculate the potential energy curve of the repulsive b 3∑+u state of the hydrogen molecule at internuclear distances R ranging from 1.0 to 12.0 bohrs. At small R, sizable improvements over the best previous calculations using elliptical coordinates are reported. The potential curve for the bound e 3∑+u state is also reported, as a by-product since it compares very well with the best conventional CI results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457045
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  • 8
    Electronic Resource
    Electronic Resource
    Monte Carlo study of free energy of hydration for Li+, Na+, K+, F−, and Cl− with ab initio potentials (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 7766-7771 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present extensive calculations of the free energies of hydration for Li+, Na+, K+, F−, and Cl− ions evaluated from Monte Carlo simulations of dilute aqueous solutions. Two-body ab initio potentials, derived from configuration interaction and self-consistent field calculations, respectively, are used for water–water and ion–water interactions. Free energy differences are calculated with the coupling parameter approach. Different numbers of sampling windows, moves per window, as well as system sizes, are investigated. It is found that: (i) if averages are taken over the forward and the backward directions of perturbation, the errors tend to cancel out; (ii) if the same number of windows and of moves per molecule are used, the spread between the two directions is much smaller for larger systems. Regarding the potentials studied, we find that although the deviation from experimental values goes from about −30% for Cl− to +21% for Na+, the overall trend is consistent with experiments and the Born theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454289
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of liquid and gaseous hydrogen selenide: Cross correlation functions (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6399-6402 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effect of the phase change from compressed gas to liquid in hydrogen selenide is explored in terms of cross correlation functions. There are considerable differences in amplitude and time dependence of the cross correlation functions which are recorded at several state points from the liquid just below the boiling point to the compressed gas. Results are obtained for 108 and 500 molecules in order to investigate the effect of sample size on cross correlation functions in the laboratory frame and in the frame (1,2,3) defined by the molecular moments of inertia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455408
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  • 10
    Electronic Resource
    Electronic Resource
    Gaussian functions in hylleraas-CI calculations. I. Ground state energies for H2, HeH+, and H+3 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2091-2093 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gaussian basis functions have been used in explicitly correlated configuration interaction calculations for the ground states of H2, HeH+, and H+3. Due to the use of rij, the polarization functions are found to be much less important in comparison with their effectiveness in the convectional CI methods. Our lowest ground state energies for H2 and HeH+ are 1.8 and 8 cm−1, respectively, above the best literature values obtained by using generalized James–Coolidge expansion in terms of confocal elliptical coordinates. With 10s and 2p contracted functions, the calculated ground state energy for H+3 is −1.343 500 hartrees, which is believed to be the lowest variational energy in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454090
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