arXiv subjects
Publications and source records attributed to C. E. Starrett.
Models of diffusion in white dwarfs universally rely on the coefficients calculated by Paquette et al. (1986). We present new calculations of diffusion coefficients based on an advanced microscopic theory of dense plasmas and a numerical simulation approach that intrinsically accounts for multiple collisions. Our method is validated against a state-of-the-art method and we present results for the diffusion of carbon ions in a helium plasma.
In Starrett and Saumon [Phys. Rev. E 87, 013104 (2013)] a model for the calculation of electronic and ionic structures of warm and hot dense matter was described and validated. In that model the electronic structure of one "atom" in a plasma is determined using a density functional theory based average-atom (AA) model, and the ionic structure is determined by coupling the AA model to integral equations governing the fluid structure. That model was for plasmas with one nuclear species only. Here we extend it to treat plasmas with many nuclear species, i.e. mixtures, and apply it to a carbon-hydrogen mixture relevant to inertial confinement fusion experiments. Comparison of the predicted electronic and ionic structures with orbital-free and Kohn-Sham molecular dynamics simulations reveals excellent agreement wherever chemical bonding is not significant.
A new approach to simulating warm and hot dense matter that combines density functional theory based calculations of the electronic structure to classical molecular dynamics simulations with pair interaction potentials is presented. The new method, which we call pseudoatom molecular dynamics (PAMD), can be applied to single or multi-component plasmas. It gives equation of state and self-diffusion coefficients with an accuracy comparable to ab-initio simulations but is computationally much more efficient.
We present a new model of warm dense matter that represents an intermediate approach between the relative simplicity of ''one-ion'' average atom models and the more realistic but computationally expensive ab initio simulation methods. Physical realism is achieved primarily by including the correlations in the plasma that surrounds a central ion. The plasma is described with the Ornstein-Zernike integral equations theory of fluids, which is coupled to an average atom model for the central ion. In this contribution we emphasize the key elements and approximations and how they relate to and expand upon a typical average atom model. Besides being relatively inexpensive computationally, this approach offers several advantages over ab initio simulations but also has a number of limitations. The model is validated by comparisons with numerical solutions for the pair distribution function of the ions from ab initio simulations for several elements and a wide range of plasma conditions. Simulations results are reproduced remarkably well and simpler limiting theories are recovered as well. This model has many potential applications to calculation of the properties of warm dense matter such as the equation of state and conductivities for a wide range of temperatures and densities.