Molecular Dynamics Study of Diffusion Coefficient for Low-Temperature Dusty Plasmas in the Presence of External Electric Fields

2022 ◽  
pp. 63-84
Author(s):  
Muhammad Asif Shakoori ◽  
Maogang He ◽  
Aamir Shahzad ◽  
Misbah Khan ◽  
Ying Zhang
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Low Temperature ◽  
Electric Fields ◽  
Integral Formula ◽  
Dusty Plasmas ◽  
Nonequilibrium Molecular Dynamics ◽  
Dust Particles ◽  
Microscopic Mechanism ◽  
Self Diffusion

The effects of external electric field (E) on the diffusion coefficient of dust particles in low-temperature dusty plasmas (LT-DPs) have been computed through nonequilibrium molecular dynamics (NEMD) simulations. The new simulation result was obtained by employing the integral formula of velocity autocorrelation functions (VACF) using the Green-Kubo relation. The normalized self-diffusion coefficient (D*) is investigated for different combinations of plasma coupling (Γ) and Debye screening (κ) parameters. The simulation outcome shows that the decreasing position of D* shifts toward Γ and also increased with the increase of κ. The D* linearly decreased with Γ and increased when applied external E increases. It is observed that the increasing trend of D* depends on the E strength. These investigations show that the present algorithm provides precise data with fast convergence and effects of κ, Γ, E. It is shown that the current NEMD techniques with applied external E can be employed to understand the microscopic mechanism of dusty plasmas.

scholarly journals Evidence for Glass Behavior in Amorphous Carbon

2020 ◽  
Vol 6 (3) ◽  
pp. 50 ◽  
Author(s):  
Steven Best ◽  
Jake B. Wasley ◽  
Carla de Tomas ◽  
Alireza Aghajamali ◽  
Irene Suarez-Martinez ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Glass Transition ◽  
Transition Temperature ◽  
Amorphous Carbon ◽  
The Self ◽  
Self Diffusion ◽  
Dynamics Simulations ◽  
Self Diffusion Coefficient ◽  
Glass Behavior

Amorphous carbons are disordered carbons with densities of circa 1.9–3.1 g/cc and a mixture of sp2 and sp3 hybridization. Using molecular dynamics simulations, we simulate diffusion in amorphous carbons at different densities and temperatures to investigate the transition between amorphous carbon and the liquid state. Arrhenius plots of the self-diffusion coefficient clearly demonstrate that there is a glass transition rather than a melting point. We consider five common carbon potentials (Tersoff, REBO-II, AIREBO, ReaxFF and EDIP) and all exhibit a glass transition. Although the glass-transition temperature (Tg) is not significantly affected by density, the choice of potential can vary Tg by up to 40%. Our results suggest that amorphous carbon should be interpreted as a glass rather than a solid.

scholarly journals Velocity autocorrelation function and self-diffusion coefficient in large molecular dynamics models of liquid argon and water

2021 ◽  
Vol 13 (2) ◽  
pp. 149-156
Author(s):  
Yuri I. Naberukhin ◽  
◽  
Alexey V. Anikeenko ◽  
Vladimir P. Voloshin ◽  
◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Autocorrelation Function ◽  
Liquid Argon ◽  
Time Interval ◽  
Velocity Autocorrelation Function ◽  
Self Diffusion ◽  
Velocity Autocorrelation ◽  
The Difference ◽  
Self Diffusion Coefficient

Autocorrelation function of the particle velocity Z(t) is calculated using the molecular dynamics method in the models of liquid argon and water. The large size of the models (more than a hundred thousand particles) allowed us to trace these functions up to 50 picoseconds in argon and up to 10 picoseconds in water, and to achieve a calculation accuracy sufficient for analytical analysis of their shape. The difference in the determination of the self-diffusion coefficient using Einstein's law and the integral of Z(t) (Green-Kubo integral) is analyzed and it is shown to be 3% at best when t is of the order of several picoseconds. The asymptote of the function Z(t) in argon is close to the power law αt–3/2 predicted by hydrodynamics, but with an amplitude that depends on the time interval under consideration. In water, the asymptote of Z(t) has nothing in common with that in argon: it has α < 0 and the exponent is close to -5/2, and not to -3/2.

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