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  • 1
    Electronic Resource
    Electronic Resource
    On decomposition of second-order Møller–Plesset supermolecular interaction energy and basis set effects (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4357-4363 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The basis set effects on the total self-consistent field (SCF) and second-order Møller–Plesset (MP2) interaction energies in the HF dimer (in the equilibrium geometry) are investigated in relation to their components: electrostatic, exchange, induction, and dispersion, calculated within the framework of intermolecular Møller–Plesset perturbation theory (IMPPT). The basis set dependence of the SCF interaction energy in the HF dimer is almost exactly determined by the electrostatic contribution. The exchange, induction, and the SCF-deformation terms are found substantially less sensitive. The MP2 correlation contribution reflects primarily the basis set dependence of dispersion. However, an accurate image of the basis set dependence is reproduced only if the electrostatic-correlation term is considered as well. Other correlation contributions: the deformation- correlation and exchange terms are found to be much less sensitive to basis set effects. All these conclusions are valid only under the condition that the supermolecular interaction energies are counterpoise-corrected for the basis set superposition error and IMPPT interaction energies are calculated with the full basis set of the dimer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457743
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  • 2
    Electronic Resource
    Electronic Resource
    Calculations of nonadditive effects by means of supermolecular Møller–Plesset perturbation theory approach: Ar3 and Ar4 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2481-2487 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nonadditive, multibody effects arising in the supermolecular Møller–Plesset perturbation theory (MPPT) (IMPPT) calculations are classified and interpreted in terms of the exchange, induction, deformation, and dispersion contributions, as defined by the perturbation theory of intermolecular forces. As an example the many-body effects in the equilateral Ar trimer and tetrahedral Ar tetramer, calculated through the MP4 level of theory with extended basis [7s4p2d], are reported and discussed. It is stressed that the "Heitler–London-exchange plus dispersion'' model for nonadditive effects is too attractive mainly because of the neglect of the second-order exchange contribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457991
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the potential energy surface of Ar–NH3 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7809-7817 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The combination of supermolecular Møller–Plesset treatment with the perturbation theory of intermolecular forces is applied in the analysis of the potential energy surface of Ar–NH3. Anisotropy of the self-consistent field (SCF) potential is determined by the first-order exchange repulsion. Second-order dispersion energy, the dominating attractive contribution, is anisotropic in the reciprocal sense to the first-order exchange, i.e., minima in one nearly coincide with maxima in the other. The estimated second-order correlation correction to the exchange effect is nearly as large as a half ΔESCF in the minimum and has a "smoothing'' effect on the anisotropy of ε(20)disp. The model which combines ΔESCF with dispersion energy (SCF+D) is not accurate enough to quantitatively describe both radial and angular dependence of interaction energy. Comparison is also made between Ar–NH3 and Ar–PH3, as well as with the Ar dimer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457249
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  • 4
    Electronic Resource
    Electronic Resource
    Intermolecular potential of the methane dimer and trimer (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4243-4253 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Heitler–London (HL) exchange energy is responsible for the anisotropy of the pair potential in methane. The equilibrium dimer structure is that which minimizes steric repulsion between hydrogens belonging to opposite subsystems. Dispersion energy, which represents a dominating attractive contribution, displays an orientation dependence which is the mirror image of that for HL exchange. The three-body correction to the pair potential is a superposition of HL and second-order exchange nonadditivities combined with the Axilrod–Teller dispersion nonadditivity. A great deal of cancellation between these terms results in near additivity of methane interactions in the long and intermediate regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458757
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  • 5
    Electronic Resource
    Electronic Resource
    Nonadditive effects in HF and HCl trimers (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7048-7056 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nonadditive effects are calculated for (HF)3 and (HCl)3 complexes and analyzed via the combination of perturbation theory of intermolecular forces with Møller–Plesset perturbation theory (MPPT). In both systems the nonadditivity is dominated by the self-consistent field (SCF) deformation effect, i.e., mutual polarization of the monomer wavefunctions. Heitler–London exchange and correlation effects are of secondary importance. Three-body terms exhibit much lesser basis set dependence than the two-body effects and even quite moderate basis sets which are not accurate enough for treatment of two-body forces can yield three-body effects of quantitative quality. This is due in large measure to the additivity of strongly basis set dependent components such as uncorrelated and correlated electrostatics and dispersion. Various approximate models for the three-body potentials and total interaction in the (HF)3 cluster are analyzed from the point of view of their ability to predict the orientation dependence of interaction energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457322
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  • 6
    Electronic Resource
    Electronic Resource
    Towards an analytical three-body potential of Ar2Cl− (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 299-308 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonadditive interactions in the Ar2Cl− cluster are studied using the supermolecular Møller–Plesset perturbation theory in conjunction with the perturbation theory of intermolecular forces. The three-body effect is rigorously dissected into fundamental nonadditive components; the exchange, the induction, and the dispersion. All three terms are important in describing nonadditivity in this cluster. The exchange nonadditivity is further divided into two terms; ES3, the electrostatic interaction between the Cl− and Ar2 subunits due to the appearance of an "exchange-quadrupole'' moment on Ar2 [Cooper and Hutson, J. Chem. Phys. 98, 5337 (1993)], and the exchange counterpart of ES3, the X3 term. ES3 term is modeled analytically using the charge-quadrupole electrostatic term. The induction nonadditivity is approximated as an interaction of induced dipoles on two Ar atoms. The three-body dispersion term is fitted to the dipole–dipole–dipole plus dipole–dipole–quadrupole expressions. The sum of all three analytical terms reproduces well the ab initio three-body potential in the region of the trimer minimum and beyond. Possible improvements in the analytical representation are also discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469642
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  • 7
    Electronic Resource
    Electronic Resource
    Ab initio study of nonadditive interactions in the Ar2HF and Ar2HCl clusters. II. Analysis of exchange and induction effects (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10708-10716 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nonadditive effects are studied in Ar2HX (X=F, Cl) clusters using the supermolecular Møller–Plesset perturbation theory in conjunction with the perturbation theory of intermolecular forces. The range of geometrical variations include the rotation of HX within the plane of the cluster and perpendicular to it. The three-body effect is rigorously dissected into the three fundamental nonadditive components: exchange, induction, and dispersion. The exchange nonadditivity is further divided into two terms: ES3, the electrostatic interaction between the HX and Ar2 subunits due to the appearance of exchange-induced quadrupole moment on Ar2 [Cooper and Hutson, J. Chem. Phys. 98, 5337 (1993)], and its exchange counterpart X3. ES3 is physically interpreted as originating from the interatomic electron exchanges within the Ar2 part. The X3 term originates from triple exchanges among all three monomers. The induction nonadditivity is dominated by the third-order effect describing the interaction of moments induced on the Ar atoms by the field of HX. This effect is faithfully represented by the multipole approximation. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468504
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  • 8
    Electronic Resource
    Electronic Resource
    Comment on "Perturbation-dependent atomic orbitals for the calculation of spin-rotation constants and rotational g tensors" [J. Chem. Phys. 105, 2804 (1996)] (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4357-4357 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473984
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  • 9
    Electronic Resource
    Electronic Resource
    Isotropy in ionic interactions. 2. How spherical is the ammonium ion? Comparison of the gas-phase clustering energies and condensed-phase thermochemistry of potassium(1+) and ammonium (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 1112-1119 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100156a018
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  • 10
    Electronic Resource
    Electronic Resource
    Ab initio study of the potential energy surface of CH4-H2O (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 3078-3089 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy surface of CH4-H2O is calculated through the fourth-order Møller–Plesset perturbation theory. In an attempt to obtain basis-set saturated values of interaction energies the extended basis sets are augmented by bond functions which simulate the effects of high-symmetry polarization functions. The absolute minimum occurs for the configuration involving the C–H-O hydrogen-bond in which O-H points toward one of the faces of the CH4 tetrahedron. The equilibrium C–O separation is equal to 6.8 a0 which corresponds to the bond energy of 0.83 kcal/mol. Due to basis set unsaturation of the dispersion energy the bond energy may still be underestimated by about 0.05 kcal/mol. The secondary minimum involving the C-H–O hydrogen-bond is some 0.2 kcal/mol less stable, and the corresponding C–O distance is longer by 0.6 a0. The anisotropy of the potential energy surface is analyzed via the perturbation theory of intermolecular forces. The binding in CH4-H2O is chiefly due to the dispersion energy which sets the general trend for the anisotropy of the surface. A more detailed examination, however, indicates that the anisotropy of the surface results from a complex interplay of various factors, including electrostatics, exchange repulsion, and to a lesser degree, the deformation effects. Analysis of various exchangeless perturbation approximations to the deformation effect indicates that the neglect of exchange component of deformation may lead to an incorrect description of the van der Waals region. The analytical potential for the CH4-H2O interaction is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465050
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