Variations in the normalized Ca II H & K and IRT line profiles as a function of T_eff, ﹩\mathrm{log}g﹩, [Fe/H], and [α/Fe], using synthetic spectra computed with the A1 configuration. The upper panels show the Ca II H line, and the lower panels show the λ8542 line. Fixed parameters are listed in the panel titles, while the varying parameter in each panel is indicated by color. The adopted parameter steps are ΔT_eff = 200 K, ﹩{\rm{\Delta }}\mathrm{log}g=0.25﹩ dex, Δ[Fe/H]=0.2 dex, and Δ[α/Fe] = 0.2 dex. V_mic and V_mac are held fixed. The gray shaded region marks the 1 Å line-core window. All wavelengths are given in vacuum, and the spectral resolving power is 300,000.