Structural Evolution and Stability Trend of Small-Sized Gold Clusters Au_n (n = 20–30)

Abstract

Structural evolution and stability pattern of pure neutral gold clusters Au n in the small size range of n = 20–30 are examined using density functional theory (DFT) calculations. The equilibrium geometries are either confirmed or determined, and some new ground state structures are identified. The most stable configurations of Au21–Au23 sizes are formed by adding extra gold atoms to the highly stable pyramidal structure of Au20, while flat-cage shapes are the best candidates for the global minima of both Au24 and Au25. For larger sizes of n = 26–30, pyramidal motifs tend to dominate the lower-lying population rather than tubular conformations as previously reported. The energy gaps, excitation energies, and exciton binding energies are also computed to test out the performance of the computational methods employed. Accordingly, a density functional with long-range exchange effects is highly recommended to quantitatively investigate both the ground and excited states of pure gold clusters.

Elucidating the binding mechanism of thione‐containing mercaptopurine and thioguanine drugs to small gold clusters

“…[27,32] Indeed, inclusion of longrange exchange effects in the LC-BLYP functional clearly improves the calculated orbital energies in noble clusters. [30,33] 3 | RESULTS AND DISCUSSION…”

Another look at energetically quasi‐degenerate structures of the gold cluster Au27q with q = 1, 0, −1

“…Of the latter, both 27a‐4 and 27a‐6 are likely to dominate the higher‐lying population. While the former can be generated by the removal of the uppermost, lowermost, and corner atoms of a regular trigonal bipyramid Au 30 , 34 the latter is formed by the addition of one extra gold atom to the most stable form of Au 26 35 . These forms are found to be around 0.3–0.4 eV higher in energy.…”

“…It should be noted that all the results discussed above are obtained at the TPSS/cc‐pVDZ‐PP level. Previous theoretical studies 34,36 pointed out that the energies of gold clusters are extremely sensitive to the density functional employed. Indeed, as can be seen from Table 1, each functional yields a profoundly different energy landscape.…”

“…Although the experimental vibrational spectra for the Au 27 0/±1 systems are not available yet, the calculated spectra are reported here as helpful predictions that may allow the optimal structures to be assigned when the spectroscopic information is available. All structures previously suggested for the Au 27 species in both neutral and ionic states are re‐optimized along with a large number of additional guess structures created by us on the basis of known structures of its immediate neighbors, that is, Au 26 and Au 28 , and the structural evolution from Au 20 to Au 30 as well 34 . We consider several types of geometrical configurations from tube‐like, star‐like shape to hollow cage and pyramidal forms.…”

Mechanism of Producing Metallic Nanoparticles, with an Emphasis on Silver and Gold Nanoparticles, Using Bottom-Up Methods

“…Recent DFT calculations [ 91 , 116 , 117 ] revealed that the mechanism of metallic nanoparticle formation, especially of AuNPs and AgNPs, consists of several steps that begin with the formation of agglomerates with M I -M I (M = Ag or Au) bonds and M 0 -M I bonds that are eventually reduced to form Ag n 0 or Au n 0 as the intermediate to AgNPs or AuNPs. Silver and gold atoms are known, respectively, to form Ag–Ag [ 118 , 119 ] and Au–Au [ 75 , 120 , 121 , 122 , 123 , 124 , 125 ] bonds and form clusters. Bond formation is also known to occur between silver atoms and silver ions [ 92 , 119 , 126 , 127 , 128 ], between silver ions [ 129 , 130 , 131 ], and between gold ions [ 80 , 120 , 131 , 132 ].…”