M. Lisal et al., Computer simulation of the thermodynamic properties of high-temperature chemically-reacting plasmas, J CHEM PHYS, 113(12), 2000, pp. 4885-4895
The Reaction Ensemble Monte Carlo (REMC) computer simulation method [W. R.
Smith and B. Triska, J. Chem. Phys. 100, 3019 (1994)] is employed to predic
t the thermodynamic behavior of chemically reacting plasmas using a molecul
ar-level model based on the underlying atomic and ionic interactions. Unlik
e previous plasma simulation studies, which were restricted to fairly simpl
e systems of fixed composition, the REMC approach is able to take into acco
unt the effects of the ionization reactions. In the context of the specifie
d molecular model, the computer simulation approach gives an essentially ex
act description of the system thermodynamics. We develop and apply the REMC
method for the test case of a helium plasma. We calculate plasma compositi
ons, molar enthalpies, molar volumes, molar heat capacities, and coefficien
ts of cubic expansion over a range of temperatures up to 100 000 K and pres
sures up to 400 MPa. We elucidate the contributions of the Coulombic forces
, ionization-potential lowering, and short-ranged interactions to the therm
odynamic properties. We compare the results with those obtained using macro
scopic-level thermodynamic approximations, including the ideal-gas (IG) and
the Debye-Huckel (DH) approaches. For the helium plasma, the short-ranged
forces are found to be relatively unimportant, but we expect these to be im
portant for molecular systems. The DH theory is always more accurate than t
he IG approximation. The DH theory yields compositions that slightly underp
redict the overall degree of ionization. For the molar heat capacity and th
e coefficient of cubic expansion, the DH theory is accurate at lower pressu
res, but at 400 MPa yields results that are up to 40% in error for the mola
r heat capacity. (C) 2000 American Institute of Physics. [S0021-9606(00)502
36-0].