Unraveling the Apparent Dimerization Tendency in Small Mo_n Clusters with n = 3–10

Abstract

The geometric, electronic, and magnetic properties of Mo n clusters, with n = 3−10, are investigated from a computational point of view. Calculations are carried out using gradient-corrected density functional theory, a small core pseudopotential to represent inner electrons, and a tripleζ basis set to describe the 4s, 4p, 4d, and 5s valence atomic orbitals. The geometries of the ground states for every cluster size are distorted versions of the familiar structures adopted by transition metal aggregates. Both the average interatomic distance and the atomization energy show a monotonic increase. In most cases metallic aggregates exhibit closed-shell electronic configurations. Only Mo 3 , Mo 8 , and Mo 10 show open-shell electronic structures. However, several isomers are found to lie within 60 meV/at above the corresponding ground state for all cluster sizes. The apparent tendency to form dimers observed by some authors in small molybdenum clusters from the dimer to the heptamer is revisited using the present methodology. In all cases an important geometrical distortion is undergone by the original clusters leading to new equilibrium geometries in which dimerization is completely absent. It is then concluded that using small core pseudopotentials is essential to obtain realistic geometries for small molydenum clusters.

NimMon (m + n = 5) Clusters for Hydrogen Electric Reduction: Synergistic Effect of Ni and Mo on the Adsorption and OH Breaking of H2O

“…The distorted trigonal bipyramid (DTB) conformation of Mo 5 in singlet is the most stable structure and this is consistent with the previous predictions and the application of small core pseudopotential in predicting small Mo clusters was proposed in those works. 37,38 The energy of triplet DTB Mo 5 is only 3.70 kcal/mol higher than that of the singlet state. The most stable structure of Ni 5 [square pyramid (SP)] is different from that predicted by B3LYP 39 while similar to the one with GGA functionals.…”

Estudio computacional del efecto promocional del cobalto en agregados aislados de Mo y Co como modelo de catalizadores de hidrodesulfuración

“…La cuarta columna consigna el número entero de átomos de Co que entran dentro de dicho rango, y la ultima columna contiene las estequiometrías resultantes. Partiendo de las estructuras obtenidas en el capítulo anterior y de estructuras bien conocidas para clústers puros de Mo [65,71], se calcularon los isómeros de menor energía para cada tamaño. Para generar las geometrías de partida se tomaron los isómeros de menor energía de cada tamaño para las geometrías originales, reemplazando cada posición no equivalente con átomos de Co, generando todas las permutaciones posibles, hasta llegar a la estequeometria deseada.…”