We present a combined experimental and theoretical study that shows the formation of one-dimensional aggregates of tetrathiafulvalene (TTF) molecules along high symmetry directions of the Cu(1 0 0) metal surface at low temperatures. Our first principles calculations permit to explain the observations. We find an adsorption geometry of the molecules in a tilted configuration that is explained as the result of a delicate balance between intermolecular and molecule-surface attractive forces of comparable strength. The inclusion of van der Waals (vdW) forces in the description is instrumental to arrive at this conclusion. (C) 2014 Elsevier B.V. All rights reserved.