The Role
of Charge States in the Atomic Structure
of Cu<sub><i>n</i></sub> and Pt<sub><i>n</i></sub> (<i>n</i> = 2–14 atoms) Clusters: A DFT Investigation
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Abstract
In general, because of the high computational
demand, most theoretical
studies addressing cationic and anionic clusters assume structural
relaxation from the ground state neutral geometries. Such approach
has its limits as some clusters could undergo a drastic structural
deformation upon gaining or losing one electron. By engaging symmetry-unrestricted
density functional calculations with an extensive search among various
structures for each size and state of charge, we addressed the investigation
of the technologically relevant Cu<sub><i>n</i></sub> and
Pt<sub><i>n</i></sub> clusters for <i>n</i> =
2–14 atoms in the cationic, neutral, and anionic states to
analyze the behavior of the structural, electronic, and energetic
properties as a function of size and charge state. Moreover, we considered
potentially high-energy isomers allowing foresight comparison with
experimental results. Considering fixed cluster sizes, we found that
distinct charge states lead to different structural geometries, revealing
a clear tendency of decreasing average coordination as the electron
density is increased. This behavior prompts significant changes in
all considered properties, namely, energy gaps between occupied and
unoccupied states, magnetic moment, detachment energy, ionization
potential, center of gravity and “bandwidth” of occupied
d-states, stability function, binding energy, electric dipole moment
and sd hybridization. Furthermore, we identified a strong correlation
between magic Pt clusters with peaks in sd hybridization index, allowing
us to conclude that sd hybridization is one of the mechanisms for
stabilization for Pt<sub><i>n</i></sub> clusters. Our results
form a well-established basis upon which a deeper understanding of
the stability and reactivity of metal clusters can be built, as well
as the possibility to tune and exploit cluster properties as a function
of size and charge