Journal of Molecular Structure, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED 244 (1991) 277-282 Elsevier Science Publishers B.V., Amsterdam 277 EMPIRICAL ENERGY PARAMETERS FOR STRUCTURAL MODELLING OF ALKALI METAL THIOCYANATE CRYSTALS IN A STANDARD FORMALISM GEORGE BRINK* and LESLIE GLASSER Department of Chemistry University of the Witwatersrand, 2050 Wits (Republic of South Africa) (Received 21 February 1990; in final form 28 June 1990) ABSTRACT Potential energy parameters describing Coulombic, van der Waals, and repulsion energies have been established for the thiocyanate ion in the EPEN/Z form of the exp-6 potential, with three ambient-stable alkali metal thiocyanate crystal structuresfor reference.A high temperatureCsSCN structure is used as a test for the potential. INTRODUCTION We have previously determined empirical constants for the interaction of the simple charged species: alkali metal and halogen ions, within alkali halide crystals [ 11, and alkaline earth ions within alkaline earth halide crystals [ 2 1, within the EPEN/B scheme of the form Coulombic plus exp-6. The intention of that work was to provide a basis for the development of consistent exp-6 sets of empirical energy parameters for complex ions. In the present paper we establish empirical energy parameters in the same Coulombic plus exp-6 en- ergy formalism for the thiocyanate ion by reference to the known crystal struc- tures of the alkali metal thiocyanates, in conjunction with the earlier-estab- lished empirical parameters for the alkali metal ions. The choice of the thiocyanate ion as a candidate for parameterization merits comment. Thio- cyanate crystals are of interest in their own right; there are 74 entries under “thiocyanate ion” in the 1913-1980 “Metal and Inorganic Indexes” of Struc- ture Reports [ 3 1. Of more direct interest to us is our involvement in a project studying the interactions of cations with crown ether type compounds. A group of papers reporting the crystal structures of alkali metal and calcium thiocya- nate complexes of 1,4,7,10,13,14,16-hexaoxacyclooctadecane [4] are the ref- *Author for correspondence. 0022-2860/91/$03.50 0 1991- Elsevier Science Publishers B.V.