Ab Initio Investigation of the Role of Atomic Radius in the Structural Formation of Pt_nTM_55–n (TM = Y, Zr, Nb, Mo, and Tc) Nanoclusters

Abstract

Platinum-based nanoclusters have been widely studied because of the possibility to tune the physical and chemical properties as a function of shape, size, chemical composition, and so forth. Although the Pt composition can be experimentally controllable, the location of the Pt species is a challenge as several physical parameters might play a role, for example, surface energy, segregation energy, atomic radius, charge transfer, strain, and so forth. Here, we report density functional theory calculations for 55-atom Pt n TM 55−n (TM = Y, Zr, Nb, Mo, and Tc) nanoalloys, which provides new insights. In general, the replacement of TM by Pt atoms increases the relative stability of the nanoalloys, and the maximum stability is reached at Pt-rich compositions (n = 35−42). From our analysis, an increase in the number of heterobonds maximizes the charge transfer among the Pt−TM species, and its magnitude depends on the electronegativity difference, coordination, and location (core or surface) of both species. For most cases, there is an electron density flow from the core to the surface region, and hence, the core is cationic, whereas the surface is anionic; however, there are few exceptions, in particular, for PtY. Thus, it yields an attractive Coulomb interaction among the chemical species and minimizes the total energy. For PtTM in which Pt is slightly larger or has a similar size as the TM atoms (Tc, Mo, and Nb), Pt atoms prefer the surface sites (smaller species are located on the core), which helps to release the strain energy. However, the charge transfer from TM to Pt helps to increase the attractive interaction between the surface and core, increasing the pressure on the core region. For PtTM in which TM (Zr and Y) is larger than Pt, contrary to what would be expected, there are some Pt atoms in the core region (including at the geometric center), resulting in a cationic surface. The release of the strain energy is obtained by symmetry breaking.

Effect of Mo on the Mechanical and Corrosion Behaviors in Non-Equal Molar AlCrFeMnNi BCC High-Entropy Alloys

“…This result is consistent with the Al 0.5 CrFe 1.5 MnNi 0.5 , which is a BCC solid solution structure in the previous study [48]. After adding Mo element, the increase in lattice constants is due to the contribution of Mo, whose radius is 141 p.m. [58], while the radii of the other elements except Al are approximately 125 p.m. [59]. Furthermore, it is noted that the (110) and ( 200 KCl) with E = -0.2412 VSHE was used as the reference electrode and a platinum sheet was used as the counter electrode.…”

“…This result is consistent with the Al 0.5 CrFe 1.5 MnNi 0.5 , which is a BCC solid solution structure in the previous study[48]. After adding Mo element, the increase in lattice constants is due to the contribution of Mo, whose radius is 141 p.m [58],. while the radii of the other elements except Al are approximately 125 p.m [59]…”

The effect of doping with pt impurity on ti clusters: a density functional theory study

“…The bimetallic clusters have been extensively investigated since the additive effect of the second metallic component in the bimetallic system due to their significant role in catalytic properties, surface segregations, etc., that emerges from the combination of nano-systems with different transition metal species [Batista et al 2018]. However, not much has been done for the Ti-bearing bimetallic clusters.…”

Investigação >i<ab initio>/i< dos mecanismos de formação de nanoflocos de dicalcogenetos de metais de transição

“…As distâncias médias de ligação foram calculadas através de uma função peso, w ij , que depende dos comprimentos de ligação entre o átomo i e seus vizinhos, aos quais se associa cada par ij às distâncias d ij . [154,155] Cacula-se neste método o peso da ligação química como maior (menor) que 1 se a ligação for menor (maior) que a distância média de ligação do átomo i com o átomo j. Desta forma, os valores de d i av para cada átomo i componente do sistema é calculado. A forma de d i av é a seguinte: As bordas de n = 9 e 12 permitem a reconstrução total das bordas dos nanoflocos, sem que haja a necessidade de distorções fora do plano devido a desencontros de átomos de Mo, como no caso do pGMCs de n = 11 para o MoSe 2 .…”