Effects of shape and dopant on structural, optical absorption, Raman, and vibrational properties of silver and copper quantum clusters: A density functional theory study

Abstract

We investigate the effects of shape and single-atom doping on the structural, optical absorption, Raman, and vibrational properties of Ag 13 , Ag 12 Cu 1 , Cu 13 , and Cu 12 Ag 1 clusters by using the (time-dependent) density functional theory. The results show that the most stable structures are cuboctahedron (COh) for Ag 13 and icosahedron (Ih) for Cu 13 , Ag 12 Cu 1core , and Cu 12 Ag 1sur . In the visible-near infrared optical absorption, the transitions consist of the interband and the intraband transitions. Moreover, red shifts are observed as follows: 1) clusters change from Ag 12 Cu 1core to Ag 13 to Ag 12 Cu 1sur with the same motifs, 2) the shapes of pure Ag 13 and Ag 12 Cu 1core clusters change from COh to Ih to decahedron (Dh), 3) the shape of Ag 12 Cu 1sur clusters changes from Ih to COh to Dh, and 4) the shapes of pure Cu 13 and Cu 12 Ag 1 clusters change from Ih to Dh to COh. All of the Raman and vibrational spectra exhibit many significant vibrational modes related to the shapes and the compositions of the clusters. The ranges of vibrational spectra of Ag 13 , Ag 12 Cu 1 or Cu 13 , and Cu 12 Ag 1 clusters become narrower and the vibrational intensities increase as the shape of the clusters changes from Ih to Dh to COh.

Alloying effect on performances of bimetallic Ag–Au cluster sensitized solar cells

“…So it is clearly found that absorption ranges of Ag-Au clusters are largest of all. Thus, alloying Ag-Au clusters can tune positions and ranges of optical peaks, which is in agreement with previous calculation on Ag-Cu [14][15][16][17][18][19][20][21][22] and Ag-Au [23,24] clusters. Therefore, alloying Ag-Au clusters also can function as a new photosensitizers for solar cell.…”

“…In particular, recently, bimetallic nanoclusters have received considerable interest recently for their particular and unique structural, electronic [9,10], optical [11,12], and magnetic properties and their importance in catalysis [13]. In our previous theoretical investigations, we calculated the optical properties of Ag-Cu [14][15][16][17][18][19][20][21][22] and Ag-Au [23,24] clusters. We found that their optical properties depend on the size, structure, and chemical ordering of their components.…”

Structures, Stabilities, Reactivities, and (Hyper)Polarizabilities of Small Gold Clusters

“…Table 1 displays the DKH2-B3PW91/DZP+1d-DKH average bond distances (R ave ) of the gold clusters, while Figure 1 shows the corresponding optimized geometries. One can note that all studied clusters prefer planar geometries, whereas Cu 7 , Cu 8 , Ag 7 , and Ag 8 are three-dimension structures. 40,41 The B3PW91 results 30 obtained with the more extensive valence basis set (BS) of the Stuttgart small-core relativistic pseudopotential are included in the 40 to Ag 2 (2.535 Å) 41 there is an enlargement of the bond distance because the electronic shielding effect overcomes the scalar relativistic effect, whereas going from Ag 2 to Au 2 the opposite occurs.…”

Pt-free silver nanoalloy electrocatalysts for oxygen reduction reaction in alkaline media

“…These studies showed that the most stable structures are generally core-shell polyicosahedra for x= 1, 7 and 6 and y= 13, 34 and 38 having a Cu core embedded in a Ag shell. 121,122 The stability of polyicosahedra core-shell geometry originates from the interplay of size mismatch, bond order-bond length correlation, and the tendency for surface segregation of Ag, due to the lower surface energy of Ag compared to Cu. 123 Ag-Cu nanoalloy clusters have revealed improved ORR activity as compared to pure Ag and Cu.…”