Eur. Phys. J. D (2013) 67: 251
https://doi.org/10.1140/epjd/e2013-40567-5

Regular Article

Structural stability, chemical order and reactivity pattern of Mo_pW_q clusters, with p + q = 8

¹ CEQUINOR, Centro de Química Inorgánica (CONICET, UNLP) Departamento de Química, Facultad de Ciencias Exactas, UNLP C.C. 962, 1900 La Plata, Argentina
² Instituto de Física “Manuel Sandoval Vallarta”, Universidad Autónoma de San Luis Potosí, S.L.P. 78000, Mexico

^a e-mail: pisdiez@quimica.unlp.edu.ar

Received: 11 September 2013
Received in final form: 11 October 2013
Published online: 10 December 2013

Abstract

The electronic structure and related properties of free-standing Mo_pW_q atomic clusters, with p + q = 8, are investigated within the framework of the fully unconstrained version of the density functional theory as implemented in the SIESTA code. Starting from the structures of the lowest-energy isomers of pure Mo₈ and W₈, they are decorated for any possible homotops and their geometries are re-optimized. Binding energies, excess energies and second differences in binding energies are reported and used to discuss relative stabilities of different isomers. Interatomic distances, magnetic moments, average coordination numbers and order parameters are also reported to achieve a better understanding of the structural evolution of the species when Mo atoms are replaced by W atoms and vice versa. Adiabatic ionization potentials, adiabatic electronic affinities and absolute hardnesses are also shown and discussed in the context of the potential reactivity of Mo_pW_q clusters against hydrotreatment processes. Those reactivity indexes suggest that the Mo₃W₅ aggregate should be a good candidate to take part in a reaction governed by a charge transfer process.