Structural stability and uniformity of magnetic Pt₁₃ nanoparticles in NaY zeolite

Abstract

Based on first-principles calculations, the structural stability and magnetic variety of Pt nanoparticles encapsulated in a NaY zeolite are investigated. Among 50 stable isomers in the gas phase, due to geometrical constraints, only about 1/3 of those clusters can be inserted in the zeolite pores. Severe structural rearrangements occur depending on whether the solid angle at the Pt vertex bound to the super-cage is larger than 2 sr (i.e., icosahedron). The most relevant example is the structural instability of the icosahedron and, when including van der Waals dispersion forces the opening of the gas phase global minimum moves towards a new L-shaped cubic wire, otherwise unstable. The total magnetisation of the encapsulated Pt decreases due to the stabilisation of less coordinated isomers, with the majority of clusters characterised by a total magnetisation of 2μ, while the majority of free clusters exhibit a threefold value. This analysis allows the understanding of the magnetic behaviour observed in recent experiments through the variety of the isomers which can be accommodated in the zeolite pore.

A Theoretical Study on the Structural, Electronic, and Magnetic Properties of Bimetallic Pt13−nNin (N = 0, 3, 6, 9, 13) Nanoclusters to Unveil the Catalytic Mechanisms for the Water-Gas Shift Reaction

“…Nonetheless, it is also reported that other metal nanoclusters from the third transition series exhibit magnetic character at a low size regime ( Yamamoto et al, 2003 ; Roduner, 2014 ). Indeed, an analysis of the results shown in Table 3 renders that our computed values for the total magnetic moment (m T ) are in close agreement with reported values in the literature ( Bartolomé et al, 2009 ; Zhao et al, 2013 ; Du et al, 2014 ; Paola et al, 2017 ).…”

“…It is already known that Pt has significant magnetic nature ( Paola et al, 2017 ; Albert and Rubin, 1964 ; Zhao et al, 2013 ; Du et al, 2014 ; Wang and Johnson, 2007 ). Also, experiments employing superconducting quantum interference device and x-ray magnetic circular dichroism have shown a magnetic behavior for Pt 13 when supported inside zeolite pores ( Roduner, 2014 ; Roduner and Jensen, 2015 ; Liu et al, 2006 ; Bartolomé et al, 2009 ), although these systems may differ from the perspective of the free nanoclusters in vacuum as discussed in the literature ( Paola et al, 2017 ). Nonetheless, it is also reported that other metal nanoclusters from the third transition series exhibit magnetic character at a low size regime ( Yamamoto et al, 2003 ; Roduner, 2014 ).…”

“… d ( Bartolomé et al, 2009 ). e computed values for vacuum, adsorbed in zeolite without D3 correction, and with D3 correction respectively ( Paola et al, 2017 ). …”

Towards operando computational modeling in heterogeneous catalysis

“…The applicability of this procedure relies on the assumption that confinement neither causes significant reordering of the gas-phase isomer stabilities nor creates entirely new isomers which are not local minima in the gas-phase. This two-phase procedure was used for Pt 13 clusters in Y zeolite, using iterative metadynamics 142 calculations to obtain low energy gas-phase Pt 13 isomers, and for small copper clusters embedded in the ERI zeolite optimized using an EA. 143 …”

Dynamics of Cluster Isomerization Induced by Hydrogen Adsorption

“…Global optimization methods also allow studying the growth and coalescence of clusters. − Another method to investigate isomeric structures of clusters consists of the comparison of the calculated and measured optical, photoelectronic, and infrared spectra . Interconversion between cluster isomers may occur when heating the clusters prior to melting, by encapsulation of the clusters in nanoporous materials or by interaction with other species …”