Formation energies and the stability of the oxides of K

Abstract

The most common valencies associated with K and O atoms are 1+ and 2 − . As a result, one expects K₂O to be the oxide of potassium which is the most stable with respect to its constituents. Calculating the formation energy within electronic structure calculations using hybrid functionals, one finds that K₂O₂ has the largest formation energy, implying the largest stability of this oxide of potassium with respect to its constituents. This is traced to the presence of oxygen dimers in the K₂O₂ structure which interact strongly resulting in a larger formation energy compared to the more ionic K₂O.