title: Quadrupole terms in the Maxwell equations: Born energy, partial molar volume, and entropy of ions.
abstract: A new equation of state relating the macroscopic quadrupole moment density Q to the gradient of the field ∇E in an isotropic fluid is derived: Q = αQ(∇E - U∇·E/3), where the quadrupolarizability αQ is proportional to the squared molecular quadrupole moment. Using this equation of state, a generalized expression for the Born energy of an ion dissolved in quadrupolar solvent is obtained. It turns out that the potential and the energy of a point charge in a quadrupolar medium are finite. From the obtained Born energy, the partial molar volume and the partial molar entropy of a dissolved ion follow. Both are compared to experimental data for a large number of simple ions in aqueous solutions. From the comparison the value of the quadrupolar length LQ is determined, LQ = (αQ/3ɛ)(1/2) = 1-4 Å. Data for ion transfer from aqueous to polar oil solution are analyzed, which allowed for the determination of the quadrupolarizability of nitrobenzene.
authors.affiliation: Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, Sofia University, 1164 Sofia, Bulgaria.
authors.forename: Radomir I
authors.initials: RI
authors.lastname: Slavchov
authors.affiliation: Theoretical Physics Department, Faculty of Physics, Sofia University, 1164 Sofia, Bulgaria.
authors.forename: Tzanko I
authors.initials: TI
authors.lastname: Ivanov