Wissing - April 5, 2018

A new equation of state for planetary impacts

Abstract: We present a new equation of state (EOS), that correctly models high pressure 
theory and fits well to experimental data of hcp-iron and the Earth. The thermal part isbased on a new formalism of the Gruneisen parameter, which improves behavior from
earlier models, bridging the gap between elasticity and thermoelasticity. The EOS is 
compared to the Tillotson EOS which is a popular EOS used in planetary impact 
simulations. We show that our EOS gives an improved behavior in the Gruneisen 
parameter and the derivative of the bulk modulus with respect to pressure. The inclusio 
of a thermodynamically consistent expanded state model and an explicit temperature 
dependence are additional improvements. We also apply the EOS to numerical 
simulations on the lunar-forming impact for comparison with previous simulations from the literature.