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Quasiclassical trajectories have been run for N 2 A 3 Σ u + + H 2 S collisions allowing for electronic transitions through surface hopping. An accurate multi-sheeted representation of the HN2 potential energy surface has been employed. For the rate constant at room temperature, we obtain 9.85 ± 0.16 × 10 - 10 cm 3 s - 1 , a value fivefold larger than the recommended experimental one. Unprecedently, we investigate the temperature dependence of the rate constant, and obtained an essentially flat Arrehenius plot. We estimate that the NH yield is at least one order of magnitude lower than the experimental upper limit.

Calcium phosphates are suggested as a CO2 adsorbent via pressure swing adsorption. Amorphous calcium phosphate (ACP) and biphasic calcium phosphate (BCP) (composed of hydroxyapatite and beta-tricalcium phosphate) were investigated for the capture/immobilization of the gas. A fluidized bed was set up to assess the levels of CO2 adsorption by ACP and BCP. A gaseous mixture was synthesized, mimicking the conditions for possible industrial use. The results show a significant reduction in CO2 concentrations. Using DFT calculations, we show that CO2 adsorption increases the stability by reducing the surface energy. The energies involved and preferential adsorption sites were also theoretically predicted.

A recent generalization of the Jahn-Teller coordinate proposed for modeling cusps on single-sheeted adiabatic potential energy surfaces for triatomics is extended to any type of crossing seam. The model is applied to the 2 A ″ state of NO 2 and the more complicated HN 2 ( 2 A ′ ) system, which shows permutationally equivalent and strongly curved seams.

A genetic algorithm coupled to electronic structure calculations is developed for searching the global minimum in the ab initio potential energy landscape of alloy clusters. The convergence criterion for the energy gradient in local optimization is progressively reduced over the generations in order to require less energy evaluations. A case studied is the Na–K alloy with MP2/ECP energies, where it is demonstrated that the algorithm is efficient in obtaining global minima. Particular analysis of a 2D–3D–2D transition in the 6-atoms case is studied in detail for the first time. Completely new structures are unveiled for larger alloy clusters.

Rate coefficients for the N ( 2 D ) + N 2 collisions were calculated employing quasiclassical trajectories and the first available set of potential energy surfaces for such excited nitrogen interactions. The details of the vibrational energy transfer are discussed, such as the contributions from reactive and non-reactive trajectories as well as the contribution of each electronic symmetry. The calculated state-to-state and state-to-all rate coefficients show that deactivation is far more probable than excitation, and multi-quanta deactivation play an important role.