The energetics of 98 atom bimetallic Pd–Pt clusters are studied using a combination of: a genetic algorithm technique (to explore vast areas of the configurational space); a basin-hopping atom-exchange routine (to search for lowest-energy homotops at fixed composition); and a shell optimisation approach (to search for high symmetry isomers). The interatomic interactions between Pd and Pt are modelled by the Gupta many-body empirical potential. For most compositions, the putative global minima are found to have structures based on defective Marks decahedra, but in the composition range from Pd₄₆Pt₅₂ to Pd₆₃Pt₃₅, the Leary tetrahedron (LT)—a structure previously identified for 98 atom Lennard-Jones clusters—is consistently found as the most stable structure. Based on the excess energy stability criterion, Pd₅₆Pt₄₂ represents the most stable cluster across the entire composition range. This structure, a T_d-symmetry LT, exhibits multi-layer segregation with an innermost core of Pd atoms, an intermediate layer of Pt atoms and an outermost Pd surface shell (Pd–Pt–Pd). The stability of the Leary tetrahedron is compared against other low-energy competing structural motifs: the Marks decahedron (Dh-M), a “quasi” tetrahedron (a closed-packed structure) and two other closed-packed structures. The stability of LT structures is rationalized in terms of their spherical shape and the large number of nearest neighbours.

Transition and noble metal clusters have proven to be critical novel materials, potentially offering major advantages over conventional catalysts in a range of value-added catalytic processess such as carbon dioxide transformation to methanol. In this work, a systematic computational study of CO₂ adsorption on gas-phase Cu_4−xPt_x (x = 0–4) clusters is performed. An exhaustive potential energy surface exploration is initially performed using our recent density functional theory basin-hopping global optimization implementation. Ground-state and low-lying energy isomers are identified for Cu_4−xPt_x clusters. Secondly, a CO₂ molecule adsorption process is analyzed on the ground-state Cu_4−xPt_x configurations, as a function of cluster composition. Our results show that the gas-phase linear CO₂ molecule is deformed upon adsorption, with its bend angle varying from about 132° to 139°. Cu_4−xPt_x cluster geometries remain unchanged after CO₂ adsorption, with the exception of Cu₃Pt₁ and Pt₄ clusters. For these particular cases, a structural conversion between the ground-state geometry and the corresponding first isomer configurations is found to be assisted by the CO₂ adsorption. For all clusters, the energy barriers between the ground-state and first isomer structures are explored. Our calculated CO₂ adsorption energies are found to be larger for Pt-rich clusters, exhibiting a volcano-type plot. The overall effect of a hybrid functional including dispersion forces is also discussed.

Controlling Ce ⁴⁺ to Ce ³⁺ electronic reducibility in a rare-earth binary oxide such as CeO ₂ has enormous applications in heterogeneous catalysis, where a profound understanding of reactivity and selectivity at the atomic level is yet to be reached.