Diffusion in liquid metals is directed by competing collective modes
| Autor: | Demmel, Franz, Jakse, Noel |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | The self-diffusion process in a dense liquid is influenced by collective particle movements. Extensive molecular dynamics simulations for liquid aluminium and rubidium evidence a crossover in the diffusion coefficient at about $1.4$ times the melting temperature $T_m$, indicating a profound change in the diffusion mechanism. The corresponding velocity auto-correlation functions demonstrate a decrease of the cage effect with a gradual set-in of a power-law decay, the celebrate {\it long time tail}. This behavior is caused by a competition of density fluctuations near the melting point with vortex-type particle patterns from transverse currents in the hot fluid. The investigation of the velocity autocorrelation function evidences a gradual transition in dynamics with rising temperature. The competition between these two collective particle movements, one hindering and one enhancing the diffusion process, leads to a non-Arrhenius-type behavior of the diffusion coefficient around $1.4~T_m$, which signals the transition from a dense to a fluid-like liquid dynamics in the potential energy landscape picture. Comment: 6 pages 4 figures |
| Databáze: | arXiv |
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