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Title: Nuclear quantum effects on the high pressure melting of dense lithium

Abstract

Using a self-developed combination of the thermodynamic integration and the ab initio path-integral molecular dynamics methods, we quantitatively studied the influence of nuclear quantum effects (NQEs) on the melting of dense lithium at 45 GPa. We find that although the NQEs significantly change the free-energies of the competing solid and liquid phases, the melting temperature (T{sub m}) is lowered by only ∼15 K, with values obtained using both classical and quantum nuclei in close proximity to a new experiment. Besides this, a substantial narrowing of the solid/liquid free-energy differences close to T{sub m} was observed, in alignment with a tendency that glassy states might form upon rapid cooling. This tendency was demonstrated by the dynamics of crystallization in the two-phase simulations, which helps to reconcile an important conflict between two recent experiments. This study presents a simple picture for the phase diagram of lithium under pressure. It also indicates that claims on the influence of NQEs on phase diagrams should be carefully made and the method adopted offers a robust solution for such quantitative analyses.

Authors:
;  [1];  [2];  [3];  [3]; ;  [1];  [4]
  1. International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871 (China)
  2. London Centre for Nanotechnology, UCL, London WC1H 0AH (United Kingdom)
  3. (United Kingdom)
  4. (China)
Publication Date:
OSTI Identifier:
22416122
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPUTERIZED SIMULATION; COOLING; CRYSTALLIZATION; FREE ENERGY; LIQUIDS; LITHIUM; MELTING; MELTING POINTS; MOLECULAR DYNAMICS METHOD; PATH INTEGRALS; PHASE DIAGRAMS; PRESSURE DEPENDENCE; SOLIDS

Citation Formats

Feng, Yexin, Chen, Ji, Alfè, Dario, E-mail: d.alfe@ucl.ac.uk, Department of Physics and Astronomy, University College London, London WC1E6BT, Department of Earth Sciences, University College London, London WC1E6BT, Li, Xin-Zheng, E-mail: xzli@pku.edu.cn, Wang, Enge, and Collaborative Innovation Center of Quantum Matter, Beijing 100871. Nuclear quantum effects on the high pressure melting of dense lithium. United States: N. p., 2015. Web. doi:10.1063/1.4907752.
Feng, Yexin, Chen, Ji, Alfè, Dario, E-mail: d.alfe@ucl.ac.uk, Department of Physics and Astronomy, University College London, London WC1E6BT, Department of Earth Sciences, University College London, London WC1E6BT, Li, Xin-Zheng, E-mail: xzli@pku.edu.cn, Wang, Enge, & Collaborative Innovation Center of Quantum Matter, Beijing 100871. Nuclear quantum effects on the high pressure melting of dense lithium. United States. doi:10.1063/1.4907752.
Feng, Yexin, Chen, Ji, Alfè, Dario, E-mail: d.alfe@ucl.ac.uk, Department of Physics and Astronomy, University College London, London WC1E6BT, Department of Earth Sciences, University College London, London WC1E6BT, Li, Xin-Zheng, E-mail: xzli@pku.edu.cn, Wang, Enge, and Collaborative Innovation Center of Quantum Matter, Beijing 100871. Sat . "Nuclear quantum effects on the high pressure melting of dense lithium". United States. doi:10.1063/1.4907752.
@article{osti_22416122,
title = {Nuclear quantum effects on the high pressure melting of dense lithium},
author = {Feng, Yexin and Chen, Ji and Alfè, Dario, E-mail: d.alfe@ucl.ac.uk and Department of Physics and Astronomy, University College London, London WC1E6BT and Department of Earth Sciences, University College London, London WC1E6BT and Li, Xin-Zheng, E-mail: xzli@pku.edu.cn and Wang, Enge and Collaborative Innovation Center of Quantum Matter, Beijing 100871},
abstractNote = {Using a self-developed combination of the thermodynamic integration and the ab initio path-integral molecular dynamics methods, we quantitatively studied the influence of nuclear quantum effects (NQEs) on the melting of dense lithium at 45 GPa. We find that although the NQEs significantly change the free-energies of the competing solid and liquid phases, the melting temperature (T{sub m}) is lowered by only ∼15 K, with values obtained using both classical and quantum nuclei in close proximity to a new experiment. Besides this, a substantial narrowing of the solid/liquid free-energy differences close to T{sub m} was observed, in alignment with a tendency that glassy states might form upon rapid cooling. This tendency was demonstrated by the dynamics of crystallization in the two-phase simulations, which helps to reconcile an important conflict between two recent experiments. This study presents a simple picture for the phase diagram of lithium under pressure. It also indicates that claims on the influence of NQEs on phase diagrams should be carefully made and the method adopted offers a robust solution for such quantitative analyses.},
doi = {10.1063/1.4907752},
journal = {Journal of Chemical Physics},
number = 6,
volume = 142,
place = {United States},
year = {Sat Feb 14 00:00:00 EST 2015},
month = {Sat Feb 14 00:00:00 EST 2015}
}