Surface Deposition Resulting from Collisions between Diglycine and Chemically Modified Alkylthiolate Self-Assembled Monolayer Surfaces

We report results from quantum mechanics/molecular mechanics (QM/MM) direct dynamics simulations of hyper-thermal collisions between N-protonated diglycine (gly(2)-H+) and a chemically modified (-COCl headgroup placed on the center chain) octanethiolate self-assembled monolayer (SAM) surfaces. Both fragmentation and reactivity are observed with the probability of each increasing with collision energy. Fragmentation occurs with a probability of 0.98 (out of 1) for a collision energy of 100 eV. Surface deposition, a subgroup of reactivity, is examined and compared to the experimental work of Laskin and co-workers (Phys. Chem. Chem. Phys. 2008, 10, 1079-90). We find that intact surface deposition is a rare event, peaking in probability at a collision energy of approximately 30-40 eV, which is in excellent agreement with experiment.