the individual species into one file before a set of models is computed. This file contains a table with over 10$^5$ wavelength points with line opacities relevant to the equation of state for 306 combinations of temperature and damping pressure $P_6$. The damping pressure is used as a proxy for the pressure that broadens metal lines by collisions with neutral atoms in cool stars. $P_6$ is the pressure of HI with the addition of the polarizability corrected pressures of neutral helium and H$_2$ (see Eq. 33 of Gustafsson et al. 2008). For each molecule, in contrast, the line opacities are given in one table for the same wavelength set, but as a function of temperature and microturbulence parameter.

The method used for the MARCS model calculations is described in detail in @gustafsson02. They start with the generation of a simplified starting model assuming a grey opacity. Physical parameters and their derivatives are computed and the model structure is iterated in a multidimensional Newton-Raphson scheme until the flux through each depth layer corresponds to the prescribed effective temperature. The models usually converged after 4 to 8 iterations; convergence also requires that the maximum temperature correction in any depth point is below 