due to increased CO in the atmosphere. The response to $\alpha$ elements is also almost the same in MARCS and ATLAS9 models. The increased $\alpha-$element content has profound effects in electron numbers and pressure for both the giant and dwarf stars, which is related to the higher number of Mg, Si, and Ca ions. Carbon rich models with C/O $>$ 1.7 and T$_{\rm eff} < 4000$K are not published here, because polyatomic carbon molecules not included in the linelists here significantly change the temperature structure in the photosphere.

These model grids will be used as the primary database for the pipeline analysing the spectra from the APOGEE survey. The high-resolution model spectra used in the survey’s atmospheric parameters and abundances determination code will be built on the models presented in this paper. Both the ATLAS9 and MARCS models atmospheres will be continuously updated with new compositions as the APOGEE survey progresses. The calculated ODFs, Rosseland opacities available for v$_{\rm t}$ = 0, 1, 2, 4, 8 km s$^{-1}$, and the ATLAS9 model atmosphere files are available for v$_{\rm t}$ = 2 km s$^{-1}$ from the ATLAS-APOGEE website[^9]. The MARCS models are available with v$_{\rm t}$ = 2 km s$^{-1}$ for 