Abstract
Despite the great success in achieving monodispersity for a great number of monolayer-protected clusters, to date little is known about the dynamics of these ultra-small metal systems, their decomposition mechanisms, and the energy that separates their structural isomers. In this work, we use density functional theory (DFT) to calculate and compare the ground state energy and the Born-Oppenheimer molecular dynamics of two well-known Au38(SCH2CH2Ph)24 nanocluster isomers. The aim is to shed light on the energy difference between the two clusters isomers and analyze their decomposition mechanisms triggered by high temperatures. The results demonstrate that the energy that separates the two isomers is of the same order of magnitude as the energy difference between the fcc and hcp phases of bulk gold reported earlier. Moreover, the MD simulations show disordering and eventual fragmentation of the cluster structures at high temperature which seem to proceed via spontaneous formation of Aux(SR)y polymeric chains. Hence, these results greatly contribute to understanding the possible decomposition mechanism, stability and robustness of existing and new monolayer-protected clusters.Graphical abstract
Highlights
Since the first reports on thiolate-passivated gold clusters [1,2,3,4], about hundred atomically precise monolayerprotected nanoclusters (MPC) have been synthesized with highly reproducible physical properties [5,6,7,8]
To validate the choice of the Au38(SCH3)24 (Au38q and Au38t) models, we calculate the density of states (DOS) of the Au38Q and Au38T clusters and compare them with the DOS of the simplified Au38q and Au38t structures
Comparing the results of Wang et al with ours we find that the energy difference between the two forms of Au38(SR)24 are of the same order of magnitude as the energy difference between the fcc phase and the metastable hcp phase of bulk gold
Summary
Since the first reports on thiolate-passivated gold clusters [1,2,3,4], about hundred atomically precise monolayerprotected nanoclusters (MPC) have been synthesized with highly reproducible physical properties [5,6,7,8]. Despite this great success, over the last few years of research in the field the latent question regarding the stability and robustness of this type of ultra-small systems has become critical.
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