Understanding structure-activity relation in VxOy clusters of varied stoichiometry and sizes through conceptual density functional approach

Pyrolysis of Mass-Selected (V2O5)NO− (N = 1−6) Clusters in a High-Temperature Linear Ion Trap Reactor

A high-temperature linear ion trap that can stably run up to 873 K was newly designed and installed into a homemade reflectron time-of-flight mass spectrometer coupled with a laser ablation cluster source and a quadrupole mass filter. The instrument was used to study the pyrolysis behavior of mass-selected (V2O5) NO− ( N = 1−6) cluster anions and the dissociation channels were clarified with atomistic precision. Similar to the dissociation behavior of the heated metal oxide cluster cations reported in literature, the desorption of either atomic oxygen atom or molecular O2 prevailed for the (V2O5) NO− clusters with N = 2−5 at 873 K. However, novel dissociation channels involving fragmentation of (V2O5) NO− to small-sized V xO y− anions concurrent with the release of neutral vanadium oxide species were identified for the clusters with N = 3−6. Significant variations of branching ratios for different dissociation channels were observed as a function of cluster size. The kinetic studies indicate that the dissociation rates of (V2O5) NO− monotonically increased with the increase of cluster size. The internal energies carried by the (V2O5) NO− clusters at 873 K as well as the energetics data for dissociation channels have been theoretically calculated to rationalize the experimental observations. The decomposition behavior of vanadium oxide clusters from this study can provide new insights into the pyrolysis mechanism of metal oxide nanoparticles that are widely used in high temperature catalysis.

Conceptual DFT and TDDFT study on electronic structure and reactivity of pure and sulfur doped (CrO3)n (n = 1-10) clusters

Different isomers of (CrO₃)_n (n = 1-10) cluster units have been investigated using Density functional approach. Their stability and reactivity has been analyzed by plotting chemical potential and HOMO-LUMO gap as a function of cluster size. The CrO₃, (CrO₃)₆ and (CrO₃)₉ are identified as the most reactive species. Reactivity of each atomic site in the cluster has been interpreted using local reactivity descriptors called Fukui Function plots. The clusters have been doped with sulfur by adding it as substitutional impurity, effect of sulfur doping has been understood by analyzing excitation energies and absorption wavelengths using time dependent-DFT(TDDFT) at CAM-B3LYP level of theory.