  This work considers two algorithms of a finite-volume solver for the MHD
equations with a real-gas equation of state (EOS). Both algorithms use a
multistate form of Harten-Lax-Van Leer approximate Riemann solver as formulated
for MHD discontinuities. This solver is modified to use the generalized sound
speed from the real-gas EOS. Two methods are tested: EOS evaluation at cell
centers and at flux interfaces where the former is more computationally
efficient. A battery of 1D and 2D tests are employed: convergence of 1D and 2D
linearized waves, shock tube Riemann problems, a 2D nonlinear circularly
polarized Alfv\'en wave, and a 2D magneto-Rayleigh-Taylor instability test. The
cell-centered EOS evaluation algorithm produces unresolvable thermodynamic
inconsistencies in the intermediate states leading to spurious solutions while
the flux-interface EOS evaluation algorithm robustly produces the correct
solution. The linearized wave tests show this inconsistency is associated with
the magnetosonic waves and the magneto-Rayleigh-Taylor instability test
demonstrates simulation results where the spurious solution leads to an
unphysical simulation.
