Abstract
A combined method of the Dirac–Hartree–Fock (DHF) method
and the reference interaction-site model (RISM) theory is reported;
this is the initial implementation of the coupling of the
four-component relativistic electronic structure theory and an
integral equation theory of molecular liquids. In the method, the DHF
and RISM equations are solved self-consistently, and therefore the
electronic structure of the solute, including relativistic effects,
and the solvation structure are determined simultaneously. The
formulation is constructed based on the variational principle with
respect to the Helmholtz energy, and analytic free energy gradients
are also derived using the variational property. The method is applied
to the iodine ion (I−), methyl iodide
(CH3I), and hydrogen chalcogenide (H2X, where X
= O–Po) in aqueous solutions, and the electronic structures of
the solutes, as well as the solvation free energies and their
component analysis, solvent distributions, and solute–solvent
interactions, are discussed.