The geometric configurations among phenylalanine derivatives (p-chlorophenylalanine, (p-CPA) thiophenylalanine (p-TPA), and p-nitrophenylalanine (p-NPA)) adsorbed on Ge(1 0 0) surfaces were investigated using density functional theory (DFT) calculations. We focused on describing the role of nucleophilic group (-Cl, -SH, and -NO2) being included in p-CPA, p-TPA, and p-NPA molecules, which can affect the stable adsorption structure energies and geometric configurations when they adsorb on the Ge(1 0 0) surface. We confirmed that geometric differences in the adsorption configurations indicated that their phenyl rings were tilted with respect to the Ge(1 0 0) surface by the effect of nucleophilicity and different sizes among -Cl, -SH and -NO2 groups. (c) 2013 Published by Elsevier B.