Among nanoscale systems, metallic nanoparticles (NPs) certainly play a primary role, due to their highly tunable properties and to the wide variety of their applications. The properties of NPs are known to strongly depend on their size and geometric shape. In the case of bimetallic nanoparticles, also known as nanoalloys, further parameters can be exploited, i.e. the NP composition and the spatial arrangement of the two atomic species within the NP volume, here referred to as chemical ordering. Within this framework, the fine control of the NP configuration (here intended as the interplay between size, shape, composition and chemical ordering) is essential in sight of the possible technological applications. To this aim, a deep understanding of the NP formation process is highly desirable: one has to clearly know what are the different stages of such process, and what are the physical forces and the chemical effects involved. Moreover, a clear knowledge of the thermodynamic stability of the produced phases under the operating conditions is desirable as well. Computer simulations can be of great help in this sense, as they can provide clear information on both the equilibrium properties and the kinetic behaviour of the NPs. Specifically, the most thermodynamically favourable configurations of a given system can be determined, and the evolution pathways can be simulated and analysed at the atomic level, therefore allowing to rationalize the experimental findings. This Ph.D. thesis is devoted to the computational study of mono- and bi-metallic NPs, with particular attention to some of the nonequilibrium phenomena undergone by them. Different examples are presented and discussed; specifically, different metallic systems are treated, all of which are of great interest due to their practical applications, and different phenomena are analysed.

Growth, coalescence and equilibration of metallic nanoparticles and nanoalloys studied by computational methods

NELLI, DIANA
2022

Abstract

Among nanoscale systems, metallic nanoparticles (NPs) certainly play a primary role, due to their highly tunable properties and to the wide variety of their applications. The properties of NPs are known to strongly depend on their size and geometric shape. In the case of bimetallic nanoparticles, also known as nanoalloys, further parameters can be exploited, i.e. the NP composition and the spatial arrangement of the two atomic species within the NP volume, here referred to as chemical ordering. Within this framework, the fine control of the NP configuration (here intended as the interplay between size, shape, composition and chemical ordering) is essential in sight of the possible technological applications. To this aim, a deep understanding of the NP formation process is highly desirable: one has to clearly know what are the different stages of such process, and what are the physical forces and the chemical effects involved. Moreover, a clear knowledge of the thermodynamic stability of the produced phases under the operating conditions is desirable as well. Computer simulations can be of great help in this sense, as they can provide clear information on both the equilibrium properties and the kinetic behaviour of the NPs. Specifically, the most thermodynamically favourable configurations of a given system can be determined, and the evolution pathways can be simulated and analysed at the atomic level, therefore allowing to rationalize the experimental findings. This Ph.D. thesis is devoted to the computational study of mono- and bi-metallic NPs, with particular attention to some of the nonequilibrium phenomena undergone by them. Different examples are presented and discussed; specifically, different metallic systems are treated, all of which are of great interest due to their practical applications, and different phenomena are analysed.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11567/1080600
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