Single ion properties by lattice energy minimisation. The perchlorate ion, ClO –4

Abstract

Single ion properties (charge distribution, “basic” radii and thermodynamic parameters) may be obtained by lattice energy calculations. The proposed theory extends current methods of determining lattice energy of complex salts by performing minimisation with respect to the individual cell lengths. Such an approach maximises the amount of information that can be obtained from crystal structure data. In this case it is used to obtain data for the perchlorate ion by consideration of the sodium, potassium and ammonium salts. We obtain: U_POT(NaClO₄)= 643 kJ mol ^–1, U_POT(KClO₄)= 599 kJ mol ^–1, U_POT(NH₄ClO₄)= 583 kJ mol^–1, ΔH^⊖_f(ClO^–₄)(g)=–344 kJ mol^–1, ΔH^⊖_hyd(ClO^–₄)(g)=–219 kJ mol^–1, [graphic omitted] = 1.86 Å for a charge distribution on the ion corresponding to q₀=–0.34.