(ricevuto il 7 Marzo 1994; approvato il 26 Aprile 1994)Summary. --We outline a theory for the metal-non-metal transition occm'ring in solutions of alkali metals in molten alkali halides as governed by a balance between the binding of ionic clusters by localized electrons and the excess free energy of an ionic assembly screened by metallic electrons. In the model the transition is driven by the composition dependence of the screening length. The theory is amenable to an analytic solution within the mean spherical approximation when Thomas-Fermi screening is used and the ions are described by charged hard spheres. Metal-molten-salt solutions and the metal-non-metal (MNM) and demixing (DM) transitions that they undergo with varying composition have attracted considerable experimental attention in recent years (for reviews see [I-3]). Related theoretical work includes evaluations of thermodynamic, structural and dynamical properties of alkali-alkali halide solutions within models which treat the valence electrons accompanying the metallic component as either forming an inert neutralizing background [4,5] or screening the ionic interactions in a linear-response approach [6][7][8], as is most appropriate in the metallic range of composition. The salt-rich end of the phase diagram has also been studied by means of first-principles computer simulations [9]. The evidence on the MNM and DM transitions has been discussed in comparison with that on metal ammonia solutions [10].In the present note we outline a liquid-structure theory of the MNM transition in these melts as arising from a balance between the free-energy gain from binding the valence electrons in localized states associated with ionic clusters and the free-energy gain from dissolving the components of such clusters into an ionic asserhbly screened by metallic electrons. We also point out a connection with the Mott criterion for MNM transitions, in which the controlling factor is the composition-dependent screening length in comparison with the size of the cluster. We consider for definiteness the case of the Kc-(KC1)I-c liquid mixture as an illustrative example, although the assumptions of the theory in its simplest formulation would probably be more appropriate to systems where the localized electronic state is more strongly bound 307
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.