Effective medium theory and Rosseland mean opacity
As a gas cools the mean opacity becomes dominated by the opacity of molecules and at low temperatures solid dust grains. Accurately computing the opacity is necessary to accurately compute the transfer of radiation through a gas. An attempt is made to refine the calculation of opacity within the stellar atmosphere modeling program PHOENIX through the addition of new optical constants, including those of the mineral species enstatite, forsterite, and fayalite. A general search for laboratory measurements of the optical constants of these minerals was performed, as well as a comparative study of the various data sets found. A study is also made investigating the importance of effective medium theory in the calculation of mean opacities within PHOENIX. Effective medium theory details the study of complex porous grains and the way in which they interact with electromagnetic radiation. The results of applying effective medium theory to modify the optical constants already within the bounds of this study are then compared to the current processes within PHOENIX. This study concludes that adding optical constants for forsterite and fayalite, and substituting a new data set for enstatite will help to improve the accuracy of PHOENIX models. Effective medium theory was found to not be a significant contributor to the calculations of the mean opacity.