Lattice self-potentials and madelung constants for some compounds

Abstract

The computerised potential and electrostatic energy calculations described in Part 1 can be used as the first step in more sophisticated calculations, four types of which are described. (i) The results obtained by calculating the actual crystal field in a sodium vacancy in NaCl are compared to the results of the familiar approximation for that situation. (ii) CaF₂ and β-alumina are used as examples of compounds in which there is remarkable similarity between some of the interstitial and some of the lattice sites. A complete calculation of all the self-potentials and the Madelung constant of β-alumina is included. (iii) In a discussion of p- and n-type semiconduction in simple binary compounds, self-potentials are used to show that many structures have a built-in preference for a deviation from stoichiometry, although other factors (not considered in this paper) can obscure this preference. (iv) The concept of a solid-state energy storage using compounds with two different cations in non-interacting sublattices is explored, using the mineral quenselite (PbMnO₂(OH)), as an example. The computer program is used to evaluate this mineral with respect to its energy density.