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Bartolomei M.,Molecular y de Agregados | Carmona-Novillo E.,Molecular y de Agregados | Hernandez M.I.,Molecular y de Agregados | Campos-Martinez J.,Molecular y de Agregados | Hernandez-Lamoneda R.,Autonomous University of the State of Morelos
Journal of Computational Chemistry | Year: 2011

Electric multipole moments, static dipole polarizabilities, and dynamic dipole, quadrupole, and mixed dipole-octupole polarizabilities of molecular oxygen and nitrogen in their ground electronic states have been obtained by means of high level multiconfigurational ab initio calculations. From these properties, we have obtained electrostatic, dispersion, and induction coefficients for the long-range interactions of the O 2O2, N 2N2, and O 2N2 dimers. Our data is a comprehensive and consistent set that for N2 N2 shows a very good agreement with previous accurate calculations, whereas for quantities involving open-shell O2 represents a considerable improvement over previous estimations. Moreover, the long-range interaction is analyzed and compared for the different interacting partners. It is found that the C8 dispersion interaction plays a nonnegligible role and that the induction component is only important for a detailed description of the highest order anisotropy terms in the spherical harmonics expansion of the long-range potential. It is also found that the total long-range interaction is quite similar in O2 O2 and O2N2, and that differences with N2N2 are mainly because of the important role of the electrostatic interaction in that dimer. Comparison with high level supermolecular calculations indicates that the present long-range potentials are accurate for intermolecular distances larger than about 15 bohr. © 2010 Wiley Periodicals, Inc.

Carmona-Novillo E.,Molecular y de Agregados | Bartolomei M.,Molecular y de Agregados | Paerez-Rios J.,Molecular y de Agregados | Campos-Martinez J.,Molecular y de Agregados | Hernandez M.I.,Molecular y de Agregados
International Journal of Quantum Chemistry | Year: 2011

An optimal procedure for obtaining spherically averaged potentials for the interaction between two linear centrosymmetric molecules (Koide and Kihara, Chem Phys 1974, 5, 34) is extended here for the calculation of the leading anisotropy term of the interaction. It is found that by computing the potential just at nine specific relative orientations of the monomers, the main anisotropy term of the spherical harmonic expansion can be calculated exactly provided that the expansion does not involve more than the first 14 terms. The approach also serves to investigate, in an affordable manner, the dependence of the interaction potential on the intramolecular degrees of freedom, and, in this way, to go beyond the commonly used rigid rotor approximation. Application has been performed for the [O2(3Σg -)]2 dimer by means of high-level ab initio calculations (RCCSD(T) method), and results are compared with a previous accurate rigid rotor potential energy surface. It is found that both the present isotropic and main anisotropy terms are very reliable and that the effect of the corrected vibrationally averaged potential is of about 1%. In addition, the dependence of the intermolecular potentials with the intramolecular vibrational modes is analyzed for the different geometries studied. The treatment can be quite useful in a realistic description of the main features of intermolecular interactions in more complex systems. © 2010 Wiley Periodicals, Inc.

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