Magnetic effects on ordering and surface segregation in NiPt nanoalloys

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2021-07, Vol.127 (7), Article 523
• Main Authors: Hizi, Abir, Said, Moncef
• Format: Article
• Language: English
• Subjects: Applied physics; Characterization and Evaluation of Materials; Condensed Matter Physics; Heisenberg theory; Intermetallic compounds; Ising model; Low temperature; Machines; Magnetic effects; Magnetism; Manufacturing; Materials science; Nanoalloys; Nanotechnology; Nickel base alloys; Nickel compounds; Optical and Electronic Materials; Physics; Physics and Astronomy; Platinum; Platinum compounds; Processes; Statistical models; Surface alloying; Surfaces and Interfaces; Thin Films
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-021-04639-x

We present a study on the effect of magnetism on the ordering and the surface segregation of NiPt surface alloys and nanoalloys having a size from 116 to 2951 atoms by means of an approach that combines a Tight Binding Ising Model (TBIM) and Heisenberg model. We find in our model via Monte Carlo simulations that the surface segregation is reversal between the dense (100) and (111) surfaces (Pt segregation) and the more opened (110) one (Ni segregation). We find also absolutely bidimensional phases such as the ( 3 × 3 ) R30(111), the c( 1 × 2 )(111), and the c( 1 × 2 )(100) ones with a core of slab pure in Ni. This is important segregation of Pt in the (111) and (100) surface (where the other sites are pure in Ni) presents an interesting behavior in catalytic applications. We study the competition between surface segregation and low temperature chemical ordering and conclude with a similar approach on truncated octahedron (TOh), cuboctahedron (CUB) and octahedron (OCT). The ( 3 × 3 ) R30(111), the c( 1 × 2 )(111), and the c( 1 × 2 )(100) phases are stable in all forms of nanoalloys (TOh, CUB, and OCT) at low-temperatures where the (111) facets are prevailing.