First sharp diffraction peak in the fragile liquid Ca0.4K0.6(NO3)1.4

Abstract

Molecular-dynamics simulations of the glass former ${\mathrm{Ca}}_{0.4}{\mathrm{K}}_{0.6}{(\mathrm{N}\mathrm{O}}_3{)}_{1.4}$ (CKN) have been performed with a polarizable model for the nitrate ion. Polarization effects in the anion were included with a fluctuating charge model. Comparison of the Ca-Ca partial radial distribution functions calculated with the polarizable model and the rigid ion model counterpart indicates that closer approach of calcium ions is allowed with the polarizable model. Typical clusters which are stabilized by ionic polarization are identified in snapshots of the simulated system. The prepeak or first sharp diffraction peak observed in the experimental static structure factor, and the associated intermediate-range order, is reproduced in the calculated structure factor provided that polarization is included in the simulation. The polarization effects on the equilibrium structure of this archetypic fragile liquid are compared to previous results on strong ionic liquids.