Structural, Ordering, and Magnetic Properties of PtNi Nanoalloys Explored by Density Functional Theory and Stability Descriptors

Abstract

Monometallic platinum and nickel nanoparticles and platinum−nickel nanoalloys are examined in the range 13−976 atoms from density functional theory calculations. A large set of competitive symmetries and morphologies are considered including the usual Mackay icosahedral, Marks decahedral, and truncated octahedral forms. A comparative analysis of relative stability order is addressed on the basis of four stability descriptors all predicted at the ab initio level from spin-polarized calculations including van der Waals interactions. For platinum nanoparticles, they unanimously conclude on the preference of truncated octahedral morphology in the range of 147−201 atoms. For nickel and platinum−nickel nanoclusters, three descriptors (cohesion energy, nanoparticle surface energy, and vibrational band center) also support such octahedral symmetry (with a skin−heart chemical ordering for nanoalloys), whereas the excess energy rather favors the icosahedral morphology (with multishell and core−shell arrangement). Such discrepancies feed the debate related to the impact of normalization on the predictive power of these descriptors and recall the high importance of validating theoretical models from a quantitative standpoint. This work invites the experimentalists to synthesize, characterize, and measure surface energetics of PtNi nanolloys in highly controlled operating conditions.

Intermetallics with sp–d orbital hybridisation: morphologies, stabilities and work functions of In–Pd particles at the nanoscale

“…), 30 for which icosahedral core-shell and multishell morphologies have been predicted to be likely for 147-923 atom NPs. 31 Compared to conventional d-d bimetallic NPs, the knowledge of systems combining transition and p-block metals -e.g. Al, Zn, Ga, Cd, In and Sn within the first periods of the periodic table -is little and is currently quickly developing.…”

“…49 Thus, numerical methods are crucial to understand, explain and predict nanoalloys' morphologies, structures and properties. 50,51 Current computational resources combined with density functional theory (DFT) are now able to calculate key quantities, like the nanoparticles' surface energy, one of the most important quantities to discuss their thermodynamic stability, 31,52,53 which can be compared to experimental measurements. 54 Because chemisorption typically involves the Fermi level of the catalysts and the HOMOs/LUMOs (highest occupied/lowest unoccupied molecular orbitals) of the reactants, the work function is one important feature for catalysis.…”

Role of Oxidizing Conditions in the Dispersion of Supported Platinum Nanoparticles Explored by Ab Initio Modeling

“…Finally, to model the Pt nanoparticles of a size larger than 1 nm, the most stable high-symmetry isomer of Pt 147 in gasphase was selected, namely a strongly irregular truncated octahedron with a diameter of ∼1.5 nm (Figure S3d). 90 This nanoparticle exhibits a variety of (100)-and (111)-type facets, offering diverse adsorption sites for oxygen atoms. The adsorption of oxygen on the nanoparticle was first examined by probing several adsorption sites for single atoms and 3-atom arrangements (see Table S5).…”

Theoretical search for characteristic atoms in supported gold nanoparticles: a large-scale DFT study

“…The atomic-scale investigation of isolated and supported nanoparticles has been conducted both experimentally 2–5 and theoretically. 6–16 First-principles density functional theory (DFT) calculations are a powerful tool to investigate the atomic and electronic structures of materials and have been widely applied to analyse catalytic reactions. However, the target system size of DFT calculations has been limited to less than a thousand atoms in most cases because the computational cost is high, scaling cubically with the number of atoms ( N atom ).…”

“…Therefore, DFT calculations have been applied mainly to clusters consisting of tens of atoms or periodic models representing the edge of nanoparticles, and there are few DFT studies on metallic particles with diameters of several nanometers. 14–16…”