Are High Heats of Atomization for Many Oxides and Fluorides of Z above 37 due to Enhanced Correlation Energy?

Abstract

Heats of atomization H_a (per atom) are compared for for 28 diatomic oxides, 14 diatomic fluorides, 26 solid and 2 polyatomic gaseous oxides, 9 solid and 5 polyatomic gaseous fluorides. There is no universal trend toward lower H_a with increasing Z in a column of the Periodic Table; d-group, post-d-group, and partly filled 4f and 5f shells encourage smaller H_a but barium, lanthanum, lutetium, hafnium, tantalum, (to the largest extent thorium), and uranium show unexpected high H_a. This 'Barium-Thorium Effect' can be rationalized by known facts of correlation energy in atoms and (light) compounds, possibly including indirect relativistic effects due to distorted AO in LCAO.