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Dependence of the multipole moments, static polarizabilities, and static hyperpolarizabilities of the hydrogen molecule on the H-H separation in the ground singlet state

Author

Miliordos, Evangelos
Hunt, Katharine L. C.
https://orcid.org/0000-0003-3471-7133

Abstract

In this work, we provide values for the quadrupole moment Theta, the hexadecapole moment Phi, the dipole polarizability alpha, the quadrupole polarizability C, the dipole-octopole polarizability E, the second dipole hyperpolarizability gamma, and the dipole-dipole-quadrupole hyperpolarizability B for the hydrogen molecule in the ground singlet state, evaluated by finite-field configuration interaction singles and doubles (CISD) and coupled-cluster singles and doubles (CCSD) methods for 26 different H-H separations r, ranging from 0.567 a.u. to 10.0 a.u. Results obtained with various large correlation-consistent basis sets are compared at the vibrationally averaged bond length r(0) in the ground state. Results over the full range of r values are presented at the CISD/d-aug-cc-pV6Z level for all of the independent components of the property tensors. In general, our values agree well with previous ab initio results of high accuracy for the ranges of H-H distances that have been treated in common. To our knowledge, for H-2 in the ground state, our results are the first to be reported in the literature for Phi for r > 7.0 a.u., gamma and B for r > 6.0 a.u., and C and E for any H-H separation outside a narrow range around the potential minimum. Quantum Monte Carlo values of Theta have been given previously for H-H distances out to 10.0 a.u., but the statistical error is relatively large for r > 7.0 a.u. At the larger r values in this work, alpha(xx) and alpha(zz) show the expected functional forms, to leading order in r(-1). As r increases further, Theta and Phi vanish, while alpha, gamma, and the components of B converge to twice the isolated-atom values. Components of C and E diverge as r increases. Vibrationally averaged values of the properties are reported for all of the bound states (vibrational quantum numbers upsilon = 0-14) with rotational quantum numbers J = 0-3. Published by AIP Publishing.