AMPA MOLECULE: CHARACTERIZATION AND ADSORPTION ON Cu SURFACES.

G. A. BOCAN; J.D. FUHR; M.L. MARTIARENA

Bariloche

Encuentro; Amicis Festum - V.H. Ponce "Advances in atomic collisions and particle-surface interactions"; 2011

p { margin-bottom: 0.08in; } Glyphosate is a widely used herbicide. This molecule is believed to be adsorbed in soils and sediments by its phosphonate group [1-3]. It also forms strong complexes with transition metals due to the presence of amino, carboxylic and phosphonic moieties [4-5]. Aminomethylphosphonic acid (AMPA) is the main product of glyphosate degradation [6-9]. In this work, we obtain a characterization of this molecule and we study the energetics of its adsorption on different Cu surfaces. Regarding the isolated molecule, we consider different configurations mentioned in the literature and obtain their vibration spectra from DFT calculations. Different implementations of the Van der Waals correction within the VASP code are tested to study how the frequencies are affected by the inclusion of this term. Finally we present preliminary results on the energetics of the adsorption of AMPA on Cu(001) and Cu(111). For both surfaces different configurations are explored and the convenience of partially deprotonizing the molecule is addressed. Dipolar corrections are introduced into the calculation and are shown to affect the prediction of the most stable adsorbed configuration. Referencias: [1] A.L. Gimsing & M. dos Santos Afonso, Biogeochemistry of chelating agents, ACS Symposium series910 (2005), 263 [2] R.L. Glass, J. Agric. Food Chem, 35 (1987), 497 [3] E. Morillo, T. Undabeytia & C. Maqueda, Environ. Sci. Technol.31 (1997), 3588 [4] T. Undabeytia, E. Morillo & C. Maqueda, J. Agric. Food Chem, 50 (2002), 1918 [5] G.A. Khoury, T.C. Gehris, L. Tribe, R.M. Torres Sánchez & M. dos Santos Afonso, Appl. Clay Sci.50 (2010),167 [6] N. Benbrahim, A. Rahmouni & M.F. Ruiz-López, Phys. Chem. Chem. Phys. 10 (2008), 5624 [7] Les dossiers Ifen, Les pesticides dans les eaux-Sixième bilan annuel-Données 2002, ET42, Institut Fraçais de l´Environement, 2004 [8] Les dossiers Ifen, Les pesticides dans les eaux-Données 2003 et 2004, D5, Institut Fraçais de l´Environement, 2006 [9] A. Ghanem, P. Bados, A.R. Estaun, L.F. De Alencastro, S. Taibi, J. Einhorn & C. Mougin, Chemosphere, 69 (2007), 1368