Dynamic structure in a molten binary alloy by ab initio molecular dynamics: Crossover from hydrodynamics to the microscopic regime
Departamento de Física Teórica, Universidad de Valladolid
- 47011 Valladolid, Spain
2 Department of Physics, Queen's University - Kingston, K7L 3N6 Ontario, Canada
Accepted: 23 January 2003
The dynamic structure factor of the liquid alloy at T=590 has been calculated by ab initio molecular-dynamics simulations using 2000 particles. For small wave vectors, , we find clear side peaks in the partial dynamic structure factors. Whereas for 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 . The mass ratio in this system, , 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 measurements (GARTRELL-MILLS P. R. et al., Physica B, 154 (1988) 1) do not show any of these modes.
PACS: 61.20.Ja – Computer simulation of liquid structure / 61.20.Lc – Time-dependent properties; relaxation / 61.25.Mv – Liquid metals and alloys
© EDP Sciences, 2003