First-principles investigation of terephthalic acid on Cu(110)

We performed first-principles calculations within the density functional theory aimed to investigate the two-dimensional geometry of one monolayer of terephthalic acid (TPA) adsorbed on Cu(110) surface. The key issue of our study is to elucidate if the molecule-molecule interactions include a hydrogen bond, since such a bond would hinder the possibility to chemically functionalize this surface [see D. S. Martin , Phys. Rev. B 66, 155427 (2002)]. In this context, our ab initio simulations are focused on the role of the spatial position of the hydrogen atom of the carboxylic group (COOH) for the structural stability of the TPA-Cu(110) system. It was found that an adsorption geometry involving a hydrogen bond is energetically unfavorable. The energy barrier separating these configurations was calculated for several different pathways of rotating the H - O bond of the carboxylate group (OCO). We also analyze the real-space topography of four different adsorption geometries by simulating scanning tunneling microscopy (STM) images for several values of the applied bias voltage (+/- 0.5, +/- 1, and +/- 2 eV). At small positive bias voltage (+/- 0.5), only two adsorption configurations can be imaged by STM. Besides this, theoretical STM images of these structures show specific feature for each case considered, and thus they can help to experimentally discriminate between the TPA-Cu(110) geometries considered in our study.