Lattice Energies from Hydration Enthalpies: Some acid-base and Structural Considerations

In the present work, using reference values for the hydration enthalpies for a series of mono, di, tri and tetra cations, as well as reference values for the lattice energies of a series of nono, di, tri and tetrahalides, it is shown that reliable lattice energies for such halides can be calculated by UPOT = (ΔHhyd+ + ΔHhyd-), by UPOT = (ΔHhyd+ + 2ΔHhyd-), by UPOT = (ΔHhyd+ + 3ΔHhyd-) or by UPOT = (ΔHhyd+ + 4ΔHhyd-) for mono, di, tri and tetrahalides, respectively. Linearized improved versions of such simply equations, parametrized in order to take into account factors such as dilution and entropic contributions, were also obtained. Lattice energies for a series of halides and other salts are calculated by using the obtained empirical equations, providing results in very good agreement with literature reference values. Furthermore, a series of empirical equations were derived, relating several acid-base parameters with lattice energy. It is shown that the cation and anion volumes (obtained by X-ray data), are very closely related with the cation and anion absolute hardness, that is, are very closely relates with the frontier (HOMO and LUMO) orbitals energies.