Relativistic free-free Gaunt factor of the dense high-temperature stellar plasma

The free-free Gaunt factor of the dense high-temperature stellar plasma is calculated by using the accurate relativistic cross section and is compared with the Gaunt factor derived by using Sommerfeld's exact nonrelativistic cross section. A wide range of electron degeneracy is accurately taken into account. Significant deviations from the nonrelativistic results are found for high-temperature cases. Results are presented in the form of extensive tables to facilitate applications.