We report DFT, semi-empirical and molecular mechanics calculations on the binding of Cu(II) to tetrapeptide DAHK, testing ability each predict coordination mode, conformation electronic spectra. • Testing computational models for predicting DAHK. LFMM generates accurate geometry but DFT required energy. Semi-empirical methods wrongly 3N2O coordination. Ligand Field Molecular Mechanics (LFMM), D...