Modeling chemical reactions in condensed phases is difficult. Interaction potentials (or force fields) like ReaxFF can perform this modeling with a high overall accuracy, but the disadvantage of ReaxFF is a low simulation speed arising from costly algorithms, in particular charge equilibration. Therefore, we reparametrized ReaxFF to incorporate Coulomb forces into other terms of the force field. Because of this change, our charge-implicit ReaxFF-CHO is >2 times faster than the original parametrization. Despite the lack of explicit electrostatic interactions, our potential can correctly model the reactions and densities of systems containing carbon, hydrogen, and oxygen atoms. We have used the new potential to simulate bombardment of trehalose by water clusters. It has been observed experimentally that these water projectiles can increase the sensitivity of secondary ion mass spectrometry by more than an order of magnitude, but no explanation for this phenomenon was given. Our simulations show that the increase in the intensity of the recorded signal coincides with the emission of trehalose–water complexes.

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Molecular dynamics computer simulations are employed to investigate processes leading to particle ejection from single-wall carbon nanotubes bombarded by keV C60 projectiles. The effect of the primary kinetic energy, the incidence angle, and the nanotube diameter on the ejection process is studied. Armchair nanotubes with diameters of 3.26, 5.4, and 8.2 nm are tested. C60 projectiles bombard these targets with kinetic energy between 3 and 50 keV and the angle of incidence ranging between 0° and 75°. The particle ejection yield is a result of the interplay between the amount of kinetic energy available for breaking interatomic bonds, the size of the bombarded area, and the size and form of projectiles hitting this area. Much of the initial kinetic energy is dissipated in the nanotubes as waves, especially for low-energy impacts. Computer simulations are used to find the optimal conditions leading to the gentle ejection of unfragmented organic molecules adsorbed on nanotube substrates. This knowledge may be helpful in the potential application of nanotube substrates in secondary ion mass spectrometry or secondary neutral mass spectrometry.

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