Thermal Properties of Co@Au CLUSTERS AND NANOALLOYS

ARNALDO RAPALLO; MARTIN LUDUEÑA, JIMENA OLMOS ASAR, OSCAR OVIEDO, ALEXIS PAZ , MARCELO MARISCAL; RICCARDO FERRANDO

Cancun

Simposio; Symposium at the XXII International Materials Research Congress; 2013

IMRC

THERMAL PROPERTIES Co@Au CLUSTERS AND NANOALLOYSMartín Ludueña3, Arnaldo Rapallo1, Jimena A. Olmos-Asar2, Oscar A. Oviedo3, Sergio. A. Paz3,Riccardo Ferrando4 and Marcelo M. Mariscal31ISMAC-Istituto per lo Studio delle Macromolecole del CNR, Via E. Bassini 15, 20133 Milano, Italy.2Dipartimento di Fisica, Universita di Trieste, Strada Costiera 11, 34151 Trieste, Italy.3INFIQC/CONICET. Departamento de Matemática y Física ? Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. X5000HUA ? Argentina. marcelo.mariscal@gmail.com4Dipartimento di Fisica, Universita di Genova, and IMEM/CNR, Via Dodecaneso 33, 16146 Genova, ItalyActually, the study of small clusters and nanoparticles (NPs) is the focus of many research areas, such as catalysis, solid state physics, physical-chemistry, biomedicine and optics, to mention some of them [1].Since thermal stability is one of the basic requirements for a NP to be used in biological applications. Therefore, it is of great importance to study the thermal behavior of pure and alloyed metal particles. In this sense, one of the most relevant aspects is the melting process, (i.e., the solid-liquid transition). It is well known that metal NPs usually have melting temperatures much lower than bulk, due to the high surface-to-volume ratio. The lowering in the melting point as the particle size decreases is a phenomenon commonly observed both at the experimental and theoretical levels [2]. From a theoretical view point, the melting of metal NPs has been studied with classical thermodynamic methods [1]. Many results show that nanoalloys can suffer complex structural transformations before the melting takes place. The simulation methods more widely employed in this field are canonical Monte Carlo and canonical Molecular Dynamics. However, comparison between these computational techniques in the literature is scarce.In this work we present the study of the melting of metal NPs with different computational techniques. We chose Co, Au and Co/Au nanoparticles as model systems, due to the high interest for applications in different fields. NPs which contain Co are chemically reactives and ferromagnetics. Due to the fact that Co Au  have Cocore-Aushell structures the less reactive and biocompatible metal is in contact with the media, whereas the Co core keeps its magnetic properties. A surprising enhancement in the thermal stability of core/shell Co13Au42 is observed compared to both pure clusters of the same size and shape [3].Studies of acoustic vibrations in NPs can provide fundamental knowledge of thermal properties.The vibrational density of states (vDOS), allows us to understand about the energy transport phenomena occurring between Core and Shell atoms. In addition, we will show preliminary results on the applications of the 2-phase model[4] to the calculation of thermodynamic properties of nanoalloys.1.R. Ferrando, J. Jellinek, and R. L. Johnston, Chemical Reviews 108, 845 (2008).2.P. Bu_at and J.-P. Borel, Phys. Rev. A 13,2287 (1976).3. A. Rapallo, J. A. Olmos-Asar, O. A. Oviedo, M. Ludueña,R. Ferrando,and M. M. Mariscal; J. Phys. Chem. C 116 (2012) 17210-172184.Shiang-Tai Lin, Mario Blanco, Willam A. Goddard III. J. Chem. Phys. 2003 119, 22P { margin-bottom: 0.21cm; }A:link { }