On a Universal Potential Energy Function and the Importance of Ionic Structures for the Ground State of Molecules

Abstract

Abstract The Kratzer-Fues-Varshni-V-potential, applied to ionic dissociation energies, is shown to yield rather accurate potential energy curves in the bonding region for H2, HF, LiH, Li2 and LiF. Vibrational levels, calculated by this ionic approximation to the ground state of widely differing molecules, nearly coincide with RKR-data. At the repulsive side of the curve and up to 2re, the agreement with RKR-curves is even better than for Morse's curve, also for the "covalent" molecules H2 and Li2. Calculated spectroscopical constants αe and ωeχe are far better than those calculated with Morse's function. Even the existence of a maximum in the potential curve at larger r-values seems not in confict with an ionic approximation. From the universal character of the function used, it is concluded that a reasonable approximation for the ground state of all molecules considered is one in terms of ionic structures, even for H2 and especially for Li2. According to the present results, the term “covalent bonding” seems to be definitely superfluous, as the usually made distinction between ionic and covalent bonding is more appearant than real.