GCMC and electronic evaluation of pesticide capture by IRMOF systems.

Environmental contamination by pesticides is a recurrent problem, and a way to minimize its impacts and provide the reduction of contaminants already in the environment is a challenge. In this context, porous materials such as metal-organic frameworks (MOFs) have gained prominence. MOFs can carry the pesticide when physically or chemically interacting with its pore sites, enabling pesticide capture. However, evaluating the best MOF to maximize the process is an important step that can be performed under computer simulation. This work used grand canonical Monte Carlo simulations to assess the interaction between glyphosate, atrazine, acephate, and dichlorodiphenyltrichloroethane pesticides with the structures of IRMOF-1, IRMOF-8, IRMOF-10, and IRMOF-16. These MOFs present several organic unit types, which generate different pore volumes with similar chemical environment. For glyphosate, atrazine, and acephate, a direct relationship was shown between the pore volume and the amount of captured pesticide, which is a direct contribution from the strong interaction between the pesticides. Higher pore volumes maximize glyphosate, atrazine, and acephate capture. Otherwise, for dichlorodiphenyltrichloroethane, the larger the pore volume, the smaller the amount of pesticide is loaded. The interaction between all pesticides and IRMOFs is mainly governed by van der Waals contribution, being more pronounced for glyphosate, atrazine, and acephate molecules.

Dynamics and spectroscopy of van der Waals complexes composed of ammonia and noble gases.

In this work, we calculate the rovibrational energies and spectroscopic constants for the systems formed by ammonia (NH3) and noble gases (Ng=He, Ne, Ar, Kr and Xe). For the spectroscopic constant calculations, we used two different methods: Dunham and another one that use rovibrational energies (here calculated by discrete variable method). In both cases, we used the improved Lennard-Jones potential energy curves (PECs). These PECs, which describe very well van der Waals systems, were built using the dissociation and equilibrium distance obtained from experiments of crossed molecular beams. The spectroscopic constant results, obtained by both methods were in excellent agreement with each other for all NH3-Ng studied systems. Also in relation to NH3-He system, we realize that although this system has a relatively small dissociation energy, it has one vibrational level. Finally, the spectroscopic constants and fundamental rovibrational energy results were used to verify the stability of each system through the lifetime decomposition.

The H + Li2 bimolecular exchange reaction: dynamical and kinetical properties at J = 0.

For the first time in the literature, rigorous time-independent quantum scattering formalism was applied, by means of the ABC program, to the H + Li(2) → LiH + Li reaction. The state-to-state probabilities as a function of the total energy have been computed at zero total angular momentum (J = 0) allowing us to evaluate the effect of vibrational/rotational excitation on the reaction promotion/inhibition, the energetic distribution of products, and the temperature dependence of the J-shifting thermal rate coefficients.