The Cotton-Mouton effect of liquid water. Part I: The dielectric  continuum model

Ruud, Kenneth; Helgaker, Trygve; Rizzo, Antonio; Coriani, Sonia; Mikkelsen, Kurt V.

doi:doi:10.1063/1.474387

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Fast, accurate semiempirical molecular orbital calculations for macromolecules

A detailed review of the semiempirical divide-and-conquer (D&C) method is given, including a new approach to subsetting, which involves dual buffer regions. Comparisons are drawn between this method and other semiempirical macromolecular schemes. D&C calculations are carried out using a basic 32 Mbyte memory workstation on a variety of peptide systems, including proteins containing up to 1960 atoms. Aspects of storage and SCF convergence are addressed, and parallelization of the D&C ...

Ab initio potential-energy surface and rotationally inelastic integral cross sections of the Ar–CH₄ complex

Symmetry-adapted perturbation theory has been applied to compute the intermolecular potential-energy surface of the Ar–CH4 complex. The interaction energy, including high-level intramonomer correlation effects, is found to be dominated by the first-order exchange contribution and the dispersion energy. The ab initio potential has four equivalent minima of ϵm = −144.30 cm−1 at Rm = 7.00 bohr, for structures in which the argon atom approaches the face of the CH4 tetrahedron. The computed potential...

We present a gauge-origin independent method for calculating the electric-field dependence of the molecular magnetizability—that is, the hypermagnetizability, related to the Cotton–Mouton Effect (CME)—of solvated molecules. In our approach, the solvated molecule is placed in a spherical cavity surrounded by a linear, homogeneous, and polarizable dielectric medium. We apply the model to investigate the dielectric-medium effects on the CME of liquid water. The effects of electron correlation, molecular geometry, and the surrounding dielectric continuum on the hypermagnetizability and the CME are investigated. The change induced in the hypermagnetizability anisotropy by the dielectric medium is the dominating effect, being almost twice as large as the correlation contribution. The combined effect of electron correlation and the dielectric continuum leads to a doubling of the hypermagnetizability anisotropy when going from the SCF gas phase value (Δη = 17.89 a.u.) to the value obtained for the MCSCF wave function in the dielectric medium (Δη = 39.74 a.u.). The effects of change in geometry are shown to be small. Our result for the static Cotton–Mouton constant averaged in the temperature range 283.15 K to 293.15 K, _mC = 15.2×10⁻²⁰ G⁻² cm³ mol⁻¹, differs from experiment still by the sign and by a factor of almost 8. The major reason for this discrepancy is the neglect of short-range interactions such as hydrogen bonding and van der Waals interactions not accounted for by the continuum model. © 1997 American Institute of Physics.