R. H. WOOD AND L. A. D’ORAZIO
2562
Thermodynamics of the Higher Oxides. 111. The Lattice Energy of Potassium Ozonide and the Electron Affinity of Ozone’
by R. H. Wood and L. A. D’Orazio Department of Chemistry, University of Delaware, Newark, Delaware
(Received JanuaTy 1.2, 1966)
The Madelung constant, van der Waals sums, and lattice energy of the potassium ozonide structure have been calculated. The results were used to evaluate the electron affinity of ozone EA (03) = 44 f 10 kcal./mole and the heat of formation of the gaseous ozonide ion A H f O (03-), = - 11 f 10 kcal./mole. The heat of formation of the hypothetical lithium ozonide is estimated (AHfO = -63 kcal./mole) and the energy of its decomposition evaluated
Introduction This paper is the third in a series on the thermodynamics of the higher oxides.2 The lattice energy of potassium ozonide has been calculated by Nikol’skii, Kazarnovskaya, Bagdasar’yan, and Kazarnovskii, who neglected the unsymmetrical charge distribution on the ozonide ion, used an estimated Madelung constant, estimated the repulsion on the basis of the Born exponent (n) of the nearest rare gas, and neglected the van der Waals forces. This paper presents a recalculation of the lattice energy using better estimates of these interactions and more recent crystallographic data.
Calculation of Madelung Constant The Madelung constant was calculated by the method of Wood4J for the crystal structure of Azaroff and Corvin.6 The symmetry is 14/mcmwith a = 8.597, c = 7.080, and with KI in a, KII in b, 01in h (z = 0.287), and 0 1 1 in k (z = 0.075, y = 0.275).’ Assuming a uniform charge distribution of - l / 3 electronic unit on each oxygen (case I) the Madelung constant is calculated to be M,(K[03]) = 2.1012 f 0.03% for the process K03(c) + K+(g) 03-(g). The Madelung constant is based on the cube root of the molecular volume (6 = 4.02908 A.). The error was estimated from the contribution of the last (third) shell (0.03%). An alternate charge distribution of o-”/”o+’/~ o-”/”(case 11) results from assuming an equal contribution from the three Lewis structures
+
c
The Journal of Physical Chemistry
‘ J
The Madelung constant for this charge distribution is M,(K[03]) = 2.2554 f
