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  • 1
    Electronic Resource
    Electronic Resource
    Hypermagnetizability anisotropy (Cotton–Mouton effect) for H2 and D2 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6686-6697 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Explicitly electron-correlated wave functions have been used to calculate the hypermagnetizability anisotropy (Δη) for H2 and D2. This property is the essential feature of the birefringence of a material in the presence of a magnetic field (the Cotton–Mouton effect). The calculations were carried out in the framework of perturbation theory and both dispersion and vibrational effects were fully taken into account. A detailed analysis of our results is made and it is concluded that electron correlation and "pure'' vibrational effects are less important than vibrational averaging and dispersion. The experimental results are only in fair agreement with our theoretical ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460245
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic optical rotation in H2 and D2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 590-599 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results are reported of the first definitive calculation of the Verdet constant for H2 and D2. This constant governs the Faraday effect. A new and compact formalism is introduced and applied with the aid of explicitly electron correlated wave functions. After ro-vibrational and thermal averaging (factors which affect the results by about 10%), our values are in good agreement with the experimental ones, which, at best, are probably only accurate to 1%. Approximations and an appropriate dispersion formula are also discussed. Our results show that for H2 and D2 the exact constant is almost exactly proportional to the so-called normal Verdet constant for the experimentally accessible frequencies. The recommended dispersion formula for H2 is V(approximately-equal-to)2.0701 ((h-dash-bar)ω/Eh)2/[0.2435−((h-dash-bar)ω/Eh)2]2×10−7 rad e a0 (h-dash-bar)−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459506
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  • 3
    Electronic Resource
    Electronic Resource
    Calculations of magnetic properties. V. Electron-correlated hypermagnetizabilities (Cotton–Mouton effect) for H2, N2, HF, and CO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 424-429 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Calculations of the hypermagnetizabilities (η) at the self-consistent-field (SCF) and second-order Møller–Plesset perturbation theory (MP2) levels of theory are reported for H2, N2, HF, and CO. Electron correlation is found to be unimportant for H2, but very important for the other three molecules. The individual components of η are more affected by correlation effects than the hypermagnetizability anisotropy (Δη) which mediates the birefringence of a material in the presence of a magnetic field (the Cotton–Mouton effect). The zero-point-vibrational averaging, pure vibrational corrections, and frequency dependence are important for the individual components, but are less important for Δη due to cancellation between the various contributions. Excellent agreement is found with the previous theoretical results for H2, but only fair agreement with the experimental results for N2 and CO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468151
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  • 4
    Electronic Resource
    Electronic Resource
    Vibrational corrections for some electric and magnetic properties of H2, N2, HF, and CO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 2180-2185 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of vibration on certain electric and magnetic properties of H2, N2, HF, and CO are reported. These properties include electric field gradients, generalized Sternheimer shielding constants, electric-field-gradient polarizabilities, nuclear shielding constants, and shielding polarizabilities. The calculations were based on both electron correlated and uncorrelated methods. Pure vibrational effects, where appropriate, were investigated as well as conventional vibrational averaging. It is found that in many cases vibration plays a very significant role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467724
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  • 5
    Electronic Resource
    Electronic Resource
    Calculation of the electric field gradients, generalized Sternheimer shielding constants, and electric-field-gradient polarizabilities for ten small molecules (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6628-6632 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electric field gradients, generalized Sternheimer shielding constants, and electric-field-gradient polarizabilities are calculated for H2, N2, F2, HF, HCl, CO, HCN, HNC, H2O, and NH3. The calculations are performed at both the Hartree–Fock and second order Møller–Plesset levels of approximation using large basis sets. For most of these molecules this is the first time that the shielding constants and electric field gradient polarizabilities have been determined. Electron correlation is generally found to be a significant factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467020
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  • 6
    Electronic Resource
    Electronic Resource
    Many-body theory of intermolecular induction interactions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4998-5010 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The second-order induction energy in the symmetry-adapted perturbation theory is expressed in terms of electron densities and polarization propagators at zero frequency of the isolated monomers. This expression is used to derive many-body perturbation series with respect to the Møller–Plesset type correlation potentials of the monomers. Two expansions are introduced—one based on the standard Møller–Plesset expansion of electron densities and polarization propagators, and the second accounting for the so-called response or orbital relaxation effects, i.e., for the perturbation induced modification of the monomer's Fock operators. Explicit orbital formulas for the leading perturbation corrections that correctly account for the response effects are derived through the second order in the correlation potential. Numerical results are presented for several representative van der Waals complexes—a rare gas atom and an ion Ar–Na+, Ar–Cl−, and He–F−; a polar molecule and an ion H2O–Na+ and H2O–Cl−; two polar molecules (H2O)2; and a rare gas atom and a polar molecule Ar–HCl and He–HCl. It is shown that in the above systems, the significance of the correlation part of the induction energy varies from a very important one in the complexes of rare gas atoms and ions to a practically negligible one in the complexes of rare gases with polar molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467218
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  • 7
    Electronic Resource
    Electronic Resource
    Calculations of magnetic properties. IV. Electron-correlated magnetizabilities and rotational g factors for nine small molecules (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2019-2026 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Calculations of the magnetizabilities and the rotational g factors at the self-consistent-field (SCF) and second-order Møller–Plesset perturbation theory (MP2) levels of theory are reported for H2, N2, F2, HF, CO, HCN, HNC, H2O, and NH3. The sums rules, that verify the reliability of the calculations, are shown to be well satisfied. The second-order correlation corrections to the magnetizabilities are found to be small, thus substantiating the generally observed good agreement between the experimental and SCF results. Vibrational corrections to the properties of the diatomic molecules are given. Very good agreement is found between the experimental and vibrationally corrected MP2 rotational g factors for the diatomic molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467234
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio potential energy surfaces for He–Cl2, Ne–Cl2, and Ar–Cl2 (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7745-7755 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The three-dimensional ground state potential energy surfaces for He–Cl2, Ne–Cl2, and Ar–Cl2 have been calculated using the single and double excitation coupled-cluster approach with noniterative perturbational treatment of triple excitations [CCSD(T)]. Calculations have been performed with the augmented correlation consistent triple zeta basis sets supplemented with an additional set of bond functions. Single point calculations for approximate minima have also been performed with several other basis sets including the quadruple zeta basis set (aug-cc-pVQZ) with bond functions. For He–Cl2 and Ar–Cl2 the CCSD(T) results show that the linear configuration is lower in energy than the T-shaped one. For Ne–Cl2 the CCSD(T) approach predicts the T-shaped configuration to be lower in energy. The linear configuration has been found to be more sensitive than the T-shaped one to the changes of the Cl–Cl bond length with the interaction becoming weaker when the Cl–Cl bond length is shortened from its equilibrium value and stronger when it is lengthened. More detailed analysis shows that sensitivity of component energies such as exchange, dispersion, and induction is much greater than that of supermolecule results. The interaction in the T-shaped configuration becomes slightly stronger for shorter Cl–Cl bonds. For He–Cl2 and Ar–Cl2 the larger zero-point vibrational energy of the linear configuration is responsible for making the T-shaped configuration the ground vibrational state. Vibrational effects further increase the difference in energy between the ground state T-shaped configuration of Ne–Cl2 and its linear counterpart. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478683
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  • 9
    Electronic Resource
    Electronic Resource
    Partitioning of interaction energy in van der Waals complexes involving excited state species: The He(1S)+Cl2(B 3Πu) interaction (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 10116-10127 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The partitioning of interaction energy between a closed-shell and an open-shell system is proposed. This allows us to describe the unrestricted Møller–Plesset interaction energy as a sum of fundamental contributions: electrostatic, exchange, induction and dispersion. The supermolecular energies derived within unrestricted Møller–Plesset perturbation theory are analyzed in terms of perturbation theory of intermolecular forces. The latter has been generalized to allow for the description of monomer wave functions within the unrestricted Hartree–Fock approach. The method is applied to the potential energy surfaces for the first excited triplet states, 3A′ and 3A″, of the He+Cl2(3Πu) complex. The 3A′ and 3A″ potential energy surfaces have different shapes. The lower one, 3A′, has a single minimum for the T-shaped structure. The higher one, 3A″, has the global minimum for the T-shaped structure and the secondary minimum for a linear orientation. The calculated well depth for the 3A′ state is 31.1 cm−1 at the 3.75 A(ring) intersystem separation at the UMP2 level with extended basis set involving bond functions. The 3A″ well depth is approximately 2.3 cm−1 smaller at this level. This order is reversed by higher correlation effects. The angular and radial behaviors of the individual components of the 3A′ and 3A″ interaction energies are compared to reveal the different nature of interaction energies in both states. A comparison with the ground state reveals that the A″ state has a typical van der Waals character similar to that of the ground state. The A′ state, on the other hand, differs considerably from the ground state. The A′ and A″ states differ primarily in different role of the intramonomer correlation effects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469913
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  • 10
    Electronic Resource
    Electronic Resource
    Ab initio study of the He(1S)+CH(X 2Π) interaction (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9525-9535 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy surfaces for the 2A′ and 2A″ states of the He(1S)–CH(X 2Π) complex were calculated using supermolecular unrestricted Møller–Plesset perturbation theory and analyzed via the relevant perturbation theory of intermolecular forces. It has been found that the two states are distinctly different. The potential energy surface (PES) of the A″ state has only a single and relatively deep minimum of De≈335 μEh for the T-shaped geometry, at R=5.0 a0 and aitch-theta=100°. The position of this minimum is determined by the exchange repulsion which is substantially reduced at this geometry. The minimum is unusually deep for a complex of He, and it can be viewed as an example of an incipient chemical bond. In contrast, the A′ state's PES represents a typical van der Waals interaction which is characterized by two similarly deep minima. The shape and location of these minima are determined primarily by the anisotropy of the dispersion component. The first minimum occurs for the collinear He–C–H arrangement, at R≈7.5 a0, and aitch-theta=0°, and is 55 μEh deep. The second minimum has a troughlike form which joins the region between R=7.5 a0, aitch-theta=140° and R=8.0 a0, aitch-theta=180°. The lowest point is approximately 54 μEh deep and occurs at R=7.5 a0 and aitch-theta=140°. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472820
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