Wave Spectra in Dusty Plasmas of Nuclear Fusion Devices

Wave’s spectra are investigated through an equilibrium molecular dynamic (EMD) simulation of three-dimensional (3D) strongly-coupled complex-dusty plasmas (SCCDPs). In this chapter, we have analyzed the correlation functions over a wide range of plasma parameters of Γ (≡1, 100) and of κ (≡4.5, 5.5) along with a higher wave’s numbers of k (≡1, 4). In EMD simulations, we have examined the propagation modes of wave in the longitudinal CL(k, t) and transverse CT(k, t) current direction at higher screening (κ). We have also analyzed the wave’s spectra in different regimes of plasma states of SCCDPs. A new simulation shows that the longitudinal (CL) and transverse (CT) waves in SCCDPs are damped for low values of Γ. However, these damping affects decrease comparatively with an increasing Γ. Outcomes show that amplitude and frequency modes of the CL and CT depend on κ, Γ, k and probably on a number of particles (N). The results obtained from EMD are in reasonable agreement with earlier known theoretical and experimental data. It has been shown that the present EMD method is the best tool for computing CL and CT in the SCCDPs over a suitable range of plasma parameters

Sound Waves in Complex (Dusty) Plasmas

Wave properties of strongly coupled complex dusty (SCCD) plasmas evaluated using the equilibrium molecular dynamics (EMD) simulation technique. In this work, the plasma normalized longitudinal current correlation function CL(k,t) and transverse current CT(k,t) are calculated for a large range of plasma parameters of Coulomb coupling parameter (Γ) and screening strength (κ) with varying wave’s number (k). In EMD simulations, we have analysed different modes of wave propagation in SCCD plasmas with increasing and decreasing sequences of different combinations of plasmas parameters (κ, Γ) at varying simulation time step (Δt). Our simulation results show that the fluctuation of waves increases with an increase of Γ and decreases with increasing κ. Additional test shows that the presented results for waves are slightly dependent on number of particles (N). The amplitude and time period of CL(k,t) and CT(k,t) also depend on different influenced parameters of κ, Γ, k and N. The new results obtained through the presented EMD method for complex dusty plasma discussed and compared with earlier simulation results based on different numerical methods. It is demonstrated that the presented model is the best tool for estimating the behaviour of waves in strongly coupled complex system (dusty plasmas) over a suitable range of parameters

Thermal Conductivity of Dusty Plasmas through Molecular Dynamics Simulations

The studies of strongly coupled complex plasmas are of significant in the area of science and technology. The plasma thermal conductivity strongly coupled (complex) plasmas is of significant in scientific technology, because it behaves as complex fluids. The two-dimensional (2D) plasma thermal conductivity of strongly coupled complex dusty plasmas (SCCDPs) has been investigated by using the homogenous nonequilibrium molecular dynamics (HNEMD) simulations, proposed by Evan-Gillan scheme, at higher screening parameter к. In our case, we have chosen particularly higher screening strength (к) for calculating plasma thermal conductivity. The new simulations of plasma thermal conductivity are computed over an extensive range of plasma states (Г, к) for suitable system sizes by applying the HNEMD simulation method at constant external force field strength (F*). It is found that the plasma thermal conductivity of SCCDPS decreases by increasing plasma states (Г, к). The calculations show that the kinetic energy of SCCDPS depends upon the system temperature (1/Г) and it is independent of к for higher screening parameter. The new results of thermal conductivity obtained from an improved HNEMD algorithm are in satisfactory agreement with earlier known numerical results and experimental data for 2D SCCDPS. It is depicted that the HNEMD method is a powerful tool to calculate an accurate plasma thermal conductivity of 2D SCCDPS

Numerical Approach to Dynamical Structure Factor of Dusty Plasmas

The dynamical structure factor [S(k,ω)] gives the information about static and dynamic properties of complex dusty plasma (CDPs). We have used the equilibrium molecular dynamic (EMD) simulations for the investigation of S(k,ω) of strongly coupled CDPs (SCCDPs). In this work, we have computed all possible values of dynamical density with increasing and decreasing sequences of plasma frequency (ωp) and wave number (k) over a wide range of different combinations of the plasma parameters (κ, Γ). Our new simulation results show that the fluctuation of S(k,ω) increases with increasing Г and it decreases with an increase of κ and N. Moreover, investigation shows that the amplitude of S(k,ω) increases by increasing screening (κ) and wave number (k), and it decreases with increasing Г. Our EMD simulation shows that dynamical density of SCCDPs is slightly dependent on N; however, it is nearly independent of other parameters. The presented results obtained through EMD approach are in reasonable agreement with earlier known results based on different numerical methods and plasma states. It is demonstrated that the presented model is the best tool for estimating the density fluctuation in the SCCDPs over a suitable range of parameters

Studies of Self Diffusion Coefficient in Electrorheological Complex Plasmas through Molecular Dynamics Simulations

A molecular dynamics (MD) simulation method has been proposed for three-dimensional (3D) electrorheological complex (dusty) plasmas (ER-CDPs). The velocity autocorrelation function (VACF) and self-diffusion coefficient (D) have been investigated through Green-Kubo expressions by using equilibrium MD simulations. The effect of uniaxial electric field (MT) on the VACF and D of dust particles has been computed along with different combinations of plasma Coulomb coupling (Γ) and Debye screening (κ) parameters. The new simulation results reflect diffusion motion for lower-intermediate to higher plasma coupling (Γ) for the sufficient strength of 0.0 < M ≥ 1.5. The simulation outcomes show that the MT significantly affects VACF and D. It is observed that the strength of MT increases with increasing the Γ and up to κ = 2. Furthermore, it is found that the increasing trend in D for the external applied MT significantly depends on the combination of plasma parameters (Γ, κ). For the lower values of Γ, the proposed method works only for the low strength of MT; at higher Γ, the simulation scheme works for lower to intermediate MT, and D increased almost 160%. The present results are in fair agreement with parts of other MD data in the literature, with our values generally overpredicting the diffusion motion in ER-CDPs. The investigations show that the present algorithm more effective for the liquids-like and solid-like state of ER-CDPs. Thus, current equilibrium MD techniques can be employed to compute the thermophysical properties and also helps to understand the microscopic mechanism in ER-CDPs

Diffusion coefficients of dusty plasmas in electric field

In this work, the effects of normalized electric field (E*) on parallel diffusion coefficients (D||) and perpendicular diffusion coefficients (D┴) are investigated through equilibrium molecular dynamics (EMD) simulations in three-dimensional strongly coupled dusty plasmas. The self-diffusion coefficients (DE) for three dimensions also have been calculated for the wide range of plasma Coulomb coupling (Γ) and Debye screening (κ) parameters with the various system sizes. The DE, D|| and D┴ are investigated using the Einstein relation with EMD simulations. The effects of constant and varying normalized E* on D|| and D┴ have been computed for the different system sizes. Simulation outcomes are outstanding in the combined effects of E* and κ and give well-matched DE, D||(E* = 0, 0.01) and D┴(E* = 0, 0.01) values at low-intermediate to large Γ with varying small-intermediate to large N. The D|| and D┴ in the limit of varying E* values are accounted for an appropriate range Γ and κ parameters. At varying E* values, it is revealed that the D|| increases and D┴ decreases with an increase in E*; however, it decreases with an increase in Γ but within statistical limits. The simple analytical temperature scaling law is tested for variation of scaled (Einstein frequency) DE, D||(E* = 0.01) and D┴(E* = 0.01). It has been shown that the present EMD simulations data obtained for the appropriate range of E* strength up to 0.01 ≤ E* ≤ 1.0 to understand the phase transitions, fundamental nature of E* linearity and anisotropy of dusty plasma systems

Thermophysical properties and condensation of R514A through molecular dynamics simulation

Hydrofluoroolefins are the latest (4th) generation of working fluids (refrigerants) due to zero ozone depletion and very low global warming potential. The R514A is a mixture of R1336mzz(Z) (74.7 %) and R1130(E) (25.3 %) and is considered a class of Hydrofluoroolefins. In this paper, the art of molecular dynamics simulation has been executed to evaluate the dynamical and thermophysical properties of R514A during the condensation process. The effects of temperatures and pressures on dynamical, thermophysical properties and condensation time are computed, analyzed and discussed. Further, the effects of the simulation time step on the properties mentioned above are computed. The simulation outcomes explained that the condensation time significantly depends on condensation temperatures and pressure values. For example, little time is required to complete the condensation cycle of R514A at lower temperatures and higher pressure, and vice versa. The changes in the structure during the condensation process also examine the in-term bonding and nonbinding interaction of R514A in vapor and liquid phases. The mean squared displacement and velocity autocorrelation function explained the average diffusion for the molecules of R1336mzz(Z) and R1130(E), and increased with respect to simulation time with increasing temperature and pressure. The obtained simulation outcomes are reliable, accurate, and in excellent agreement with previously available simulation data. Current investigations indicated that the refrigerant R514A considering sustainable and eco-friendly in numerous applications in the replacement of R123