Line profiles of Na I 6154 Å, Mg I 4730 Å, Al I 6696 Å and Si I 5772 Å computed using different hydrogen collision models: QM (black lines), EFM (red lines), DRW, S_H = 0.1 (blue lines), DRW, S_H = 0.1 (olive lines) and DRW, S_H = 0.002 for Al I (magenta lines). The lines were computed at T_eff = 4500, log ɡ = 2.5 and for two metallicities, [Fe/H] = +0.00 (left panels) and [Fe/H] = −3.00 (right panels). The χ² differences obtained between each model relative to the QM are shown on the plots.