Integral equation calculations and computer simulations of the static structure and ionic transport in molten thallium halides

Abstract

We present the first calculations and computer simulations of the static structure and ionic transport properties of molten thallium halides near melting. The calculations have been carried out using the hypernetted-chain theory of liquids (HNC), and for the simulations we have used molecular dynamics (MD). The potentials used for the calculations have the same functional form as the semiempirical potential originally proposed by Vashishta and Rahman (Vashishta P and Rahman A 1978 Phys. Rev. Lett. 40 1337) for studying . The total structure factors obtained from our calculations are in fair qualitative agreement with available neutron scattering data. The local structures of these melts exhibit a behaviour intermediate between those of the noble-metal halides and the alkali halides. The mean square displacements, velocity autocorrelation functions and distinct correlation functions confirm further this intermediate behaviour suggesting a rather complicated diffusion mechanism where mass and size effects compete strongly. The results for the specific ionic conductivities are in good agreement with experiment if it is assumed that the ions, in their transport, have an integer charge of magnitude | Z | = 1, rather than the magnitude of the effective charges used in the potentials.