Journal
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
Volume 63, Issue 6, Pages -Publisher
SCIENCE PRESS
DOI: 10.1007/s11433-019-1466-2
Keywords
molecular dynamics; numerical methods; solid-liquid transitions; laser ablation of solids
Categories
Funding
- National Key RAMP
- D Program of China [2017YFA0403200]
- National Natural Science Foundation of China [11774429]
- NSAF [U1830206]
- Science Challenge Project [TZ2016001]
- Science and Technology Project of Hunan Province [2017RS3038]
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With the highly optimized embedded-atom-method (EAM) potential and electron-phonon coupling factor obtained from experimental data, the dynamics of the formation of warm dense gold and the nuclear response of gold foils upon intense laser excitation were investigated using two-temperature molecular dynamics simulations. Considering laser energy densities ranging from 0.18 to 1.17 MJ/kg, we provide a microscopic picture of the formation of warm dense gold. A threshold (0.19 MJ/kg) for the laser energy density was determined, identifying two different melting mechanisms. For an energy density below 0.19 MJ/kg, the melting of the foil is controlled by the propagation of melt fronts from external surfaces, which results in heterogeneous melting on the time scale of hundreds of picoseconds. For an energy density above 0.19 MJ/kg, homogeneous nucleation and growth of liquid regions inside the foil play the leading role, and homogeneous melting occurs with several picoseconds. Compared with previous simulations and experimental measurements, the evaluated different threshold value indicates that the improvement in the electron heat capacity for the two-temperature model by including the kinetic information of electrons may predict better laser-matter interactions under such extreme non-equilibrium conditions.
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