Relativistic density functional theory (DFT) based molecular dynamical simulations are performed on gold clusters with 3–10 atoms (Au
n
, n = 3–10) with an aim of understanding their finite temperature behavior. Conformations of a cluster coexisting at different temperatures are analyzed. The simulations reveal that the finite temperature behavior of Au clusters can be classified into three regions, viz., a “solid-like” region, a “structural fluctionality” region, and a “liquid-like” state. The structural fluctionality region is when the cluster dynamically interconverts between two conformations through a metastable intermediate. For Au
n
, n ≤ 7, where the atoms reorient continuously such that two planar conformations coexist. On the other hand, for Au
n
, n ≥ 8, the cluster behaves as a quasi-planar liquid where the outer edge atoms of the cluster bend and relax alternatively around a central planar region. In liquid-like state the cluster is predominantly in a 3D conformation and transits through various conformations. The onset and duration of each of the above three regions are seen to be size dependent. Au6 is the most stable cluster and remains in its ground state conformation (or solid-like region) up to nearly 1100 K. Au9 is the least stable among the studied clusters with a liquid-like state around room temperature itself. All the clusters with the exception of Au6 enter the liquid-like state at much lower temperatures as compared to that of bulk gold.
Relativistic density functional theory (DFT) based calculations have been performed on gold clusters with six to thirteen atoms (Au
n
; n = 6−13). The ground state geometries of these clusters as obtained from our calculations are presented and discussed. This work proposes that atoms in a ground state conformation can be classified into distinct types of reactive sites in a given geometry. Based on symmetry, susceptibility of various types of reactive sites in the ground state geometry toward an impending electrophilic and/or a nucleophilic attack has also been studied using DFT based reactivity descriptors. The studies have also been extended to high energy isomers in these cluster sizes. The reactivity of various sites as a function of cluster size and shape was thus analyzed. The study shows that as a general rule the size and shape of the cluster influences the number and position of available sites for an electrophilic and/or nucleophilic attack. This makes the reactivity patterns of these clusters highly complex. The study also highlights as to how for a cluster with seven atoms (Au7) various conformations are likely to coexist indicating that the reactivity patterns of various high energy conformations are also important while dealing with small sized Au clusters.
The influence of relativistic effects on the structure, vibrational modes, and reactivity of recently discovered tertrahedral gold clusters (Au 19 and Au 20 ) are investigated using density functional methods. The intramolecular reactivity of the clusters was analyzed using density functional-based reactivity descriptors. The work shows that whereas the structural properties and vibrational modes are considerably affected by the relativistic effects, the reactivity trends based on Fukui function calculation on various atoms within this cluster remain unaffected by the absence or presence of relativistic effects. The reactivity descriptors reveal that the vertex atoms are the most reactive ones in Au 20 toward a nucleophilic attack. On the other hand, atoms connecting the missing vertex edge with the pyramid base along with the vertex atom are the most reactive for a nucleophilic attack in Au 19 . The atoms lying at the center of each face are favorable for an electrophilic attack in both cases. Interestingly, the atoms with a missing cap in Au 19 are highly favorable for electrophilic attack, and Au 20 has more sites for a favorable nucleophilic attack.
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