Collisional and transport parameters of Cu in the Warm Dense Matter regime calculated using the Average Atom Model

Collisional and transport parameters for Cu are computed using the Average Atom Model. Transition metals such as copper are difficult to model within the framework of the Average Atom Model due to the presence of a narrow band of 3d electrons that mix and hybridize with the broad 4s band of nearly-free electrons. With electron temperature increasing, the 3d electrons play a key role in the thermodynamics and transport properties of Cu [Z. Lin, et. al., Phys. Rev. B 77, 075133 (2008)]. In this work, the Average Atom Model was used to track the average energy of the 3d band and its evolution with electron temperature. At room temperature, its center is at ~6 electron-volts (eV), a few electron-volts below the Fermi energy, and with electron temperature increasing it sinks relative to it. At electron temperature of about 8 eV the energy of the 3d electrons leave the conduction band. A long-standing problem related to the average ion charge observed by conduction band electrons is addressed and successfully resolved. A work-around has been found that predicts the correct average ion charge, , by formally introducing a third group of electrons: quasi-bound electrons. Benchmarking with published data has been made that shows good agreement.