Comparison between the synthetic spectrum with stellar parameters T_eff = 4200 K, log g = 1.4, and [M/H] = 0.0 dex (the black solid line) and the corrispondent spectrum model (the gray solid line) constructed by SP_Ace using the EWs corrected for the opacity of the neighbor lines as described in Sect. 5.3. The dotted line is the spectrum model constructed using the EW of the lines computed as if they were isolated (i.e., no correction for the opacity of the neighbor lines). Plus, cross, and triangle symbols indicate the position of the Fe , V , and Ni  lines, respectively.