Molecular dynamics simulations of optical conductivity of dense plasmas

Abstract

The optical conductivity sigma (omega) for dense Coulomb systems is investigated using molecular dynamics simulations on the basis of pseudopotentials to mimic quantum effects. Starting from linear response theory, the response in the long-wavelength limit k=0 can be expressed by different types of autocorrelation functions (ACF's) such as the current ACF, the force ACF, or the charge density ACF. Consistent simulation data for transverse as well as longitudinal ACF's are shown which are based on calculations with high numerical accuracy. Results are compared with perturbation expansions which are restricted to small values of the plasma parameter. The relevance with respect to a quantum Coulomb plasma is discussed. Finally, results are presented showing a consistent description of these model plasmas in comparison to quantum statistical approaches and to experimental data.

Bound State Formation and Optical Properties of Partially Ionized Dense Plasmas

“…In order to compare with the quantum statistical calculation, classical MD simulations have to be performed on the basis of a pseudo-potential which accounts for quantum effects at short interaction distances. A systematic analysis of MD simulations has been performed with respect to the dynamical structure factor [9] as well as the dc conductivity [1,10,11]. It was found that the analytical quantum statistical results are good approximations as long as Γ = e 2 /(4π 0 k B T )(4πn/3) 1/3 ≤ 1.…”

Spatially resolved dynamic structure factor of finite systems from molecular dynamics simulations

“…which can be evaluated using quantum statistical approaches such as Green function theory, see [49], or numerical approaches such as MD simulations, see [50]. As collisions are relevant in strongly correlated systems, the dynamical collision frequency ν(ω) is derived and appears in a generalized Drude formula [51,52] …”

“…Exemplarily, we refer to [50]. The state of a homogeneous one-component plasma in thermodynamic equilibrium is characterized by the nonideality parameter Γ = e 2 (4πn e /3) 1/3 (4πε 0 k B T e ) −1 and the degeneracy parameter Θ = 2m e k B T eh −2 (3π 2 n e ) −2/3 , T e is the temperature of the electrons.…”

Collective and static properties of model two-component plasmas

“…Further extension of the present mixed approach to more recent data for the model systems described by other effective potentials [5,25] is planned. Table I, but for Γ = 0.5, r s = 1.…”

“…(dashed) and quantal calculations (solid). In the classical case, the kinetic contribution is approximated by the Vlasov term (25), whereas in the quantal case expression (26) is used. …”