Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

Numerical Heat Transfer, Part A: Applications

2017

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By combining ab initio quantum mechanics calculation and Drude model, electron temperature and lattice temperature dependent electron thermal conductivity is calculated and implemented into a multiscale model of laser material interaction, which couples the classical molecular dynamics and two-temperature model. The results indicated that the electron thermal conductivity obtained from ab initio calculation leads to faster thermal diffusion than that using the electron thermal conductivity from empirical determination, which further induces deeper melting region, larger number of density waves travelling inside the copper film and more various speeds of atomic clusters ablated from the irradiated film surface.

Section: Modeling and Simulationmentioning

confidence: 99%

Multiscale modeling of femtosecond laser irradiation on a copper film with electron thermal conductivity from ab initio calculation

Numerical Heat Transfer, Part A: Applications

2017

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“…The local density approximation (LDA) was employed in calculating the exchange and correlation energy. After convergence test, a plane wave cutoff of 28 and a Monkhorst Pack mesh of 10 10 10 -point were adopted in the FT-DFT calculation. Fifty bands were set to allow sufficient states to be occupied of during the high laser energy excitation of electrons.…”

Section: Simulation Detailsmentioning

confidence: 99%

“…Pure ab initio quantum mechanics (QM) MD simulation liberated the empirical description of the interatomic penitential in classical MD and took the role of femtosecond laser pulse excitation of electrons into account [20,26,27]. Nevertheless, the size of simulated system in ab initio quantum mechanics MD is limited in tens to hundreds of atoms, due to the expensive computational cost [28,29].…”

Section: Introductionmentioning

confidence: 99%

Melting and thermal ablation of a silver film induced by femtosecond laser heating: a multiscale modeling approach

2017

Appl. Phys. A

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The femtosecond laser pulse heating of silver film is investigated by performing quantum mechanics (QM), molecular dynamics (MD) and two temperature model (TTM) integrated multiscale simulation. The laser excitation dependent electron thermophysical parameters (electron heat capacity, electron thermal conductivity, and effective electron-phonon coupling factor) are determined from ab initio QM calculation, and implemented into TTM description of electron thermal excitation, heat conduction, as well as electron-phonon coupled thermal energy transport. The kinetics of atomic motion is modeled by MD simulation. Energy evolution of excited electron subsystem is described by TTM in continuum. The MD and TTM are coupled by utilizing the effective electron-phonon coupling factor. Laser heating with varying laser fluence is systematically studied to determine the thresholds of the homogeneous melting and ablation. The thermal ablation induced by faster expansion of locally and excessively superheated silver is reported. This paper provides a basis for interpreting the phase change process induced by laser heating, and facilitates the advancement of femtosecond laser pulse processing of material.

“…Owing to the unique merit of little collateral damage [1,2], femtosecond laser pulse processing of material has the advantage over conventional laser machining, which makes it as a widely acknowledged approach in micromachining and microfabrication. With the miniaturization of the objective material to nanoscale, plenty of challenges to the conventionally macroscopic heat transfer theories come up [3][4][5][6]. When the laser pulse duration is comparable to the timescales of ultrafast laser irradiation induced thermal and mechanical response, the factors leading to laser spallation and ablation become complex.…”

Section: Introductionmentioning

confidence: 99%

Effects of Film Thickness on Femtosecond Laser Spallation and Ablation of Silver Film

Proceeding of Second Thermal and Fluids Engineering Conference

2017

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Ab initio quantum mechanics, classical molecular dynamics and two-temperature model integrated multiscale simulation is carried out to study the effects of film thickness on the femtosecond laser spallation and ablation of silver film. At an interval of 130.7296 , five silver films with increasing thickness from 392.1888 to 915. 1072 are simulated. The simulation results show that film thickness has close correlation with the Kelvin degree of heating of the laser irradiated silver films, which further affects the laser spallation and ablation.