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Dynamic structure in a molten binary alloy by ab initio Molecular Dynamics: Crossover from Hydrodynamics to the Microscopic Regime

D. J. Gonzalez·L. E. Gonzalez·J. M. Lopez·M. J. Stott
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Abstract

The dynamic structure factor of the 7Li0.61Na0.39 liquid alloy at T=590 K has been calculated by ab initio molecular dynamics simulations using 2000 particles. For small wavevectors, 0.15 <= q/A-1 <= 1.6, we find clear side peaks in the partial dynamic structure factors. Whereas for q <= 0.25 A-1 the peak frequencies correspond to the hydrodynamic sound dispersion of the binary alloy, for greater q values we obtain two modes with phase velocities above and below the hydrodynamic sound. A smooth transition between hydrodynamic sound and the two collective modes is shown to take place in the range 0.25 <= q/A-1 <= 0.35. The mass ratio in this system, mNa/mLi = 3, is the smallest one so far for which the fast mode is observed. We also predict that inelastic X-ray scattering experiments would be able to detect the slow mode, and explain why the inelastic neutron scattering experiments [P.R. Gartyrell-Mills et al, Physica B 154, 1 (1988)] do not show any of these modes.

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D. J. Gonzalez, L. E. Gonzalez, J. M. Lopez, M. J. Stott. 2002-08-08. Dynamic structure in a molten binary alloy by ab initio Molecular Dynamics: Crossover from Hydrodynamics to the Microscopic Regime. https://doi.org/10.1209/epl%2Fi2003-00357-4

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