Effect of the character of the (Ni, Pd) cluster/graphene interatomic bonds on the thermosize effects and structural-isomeric transitions

Stability and thermal evolution of transition metal and silicon clusters

“…These rearrangements, classified as isomerization, preceded the proper melting, the initial stage of which was the appearance of adatoms and vacancies. 81 ± 84 Polukhin et al 64,67 employed MD simulation of the thermal evolution of perfect Ni N and Pd N nanoclusters comprising 13 to 561 atoms and having different initial structures (fcc, bcc or Ih) upon stepwise heating (50 K steps) from 300 to 1350 K.…”

“…The mechanism of melting of such clusters is more complicated than the melting mechanism of macroscopic crystals: in the nanorange, melting starts at temperatures that are less than half the crystal melting point, proceeds over a wider temperature range (*1/3 of the heating range) and comprises several stages. 67,74 The nanosize effects in the clusters Ð small objects with marked density fluctuations and continuous redistribution of the kinetic and potential energy Ð start to be manifested before melting as structural transitions with continuous interconversion of coordinations (isomerization) and the loss of structure stability.…”

“…The bonds formed upon the contact of graphene with most transition metals are weaker than covalent bonds but stronger than van der Waals interactions. 67 In terms of strength of interaction with graphene, metal atoms can be conventionally classified into two types:…”

“…67 In ring clusters as the sites of the moire structure being formed, transitions from the planar network of the graphene C = C double bonds to a tetrahedral network of C7C single bonds are possible.…”

“…Under the action of interactions determined by the nature of sorption (chemisorption or adsorption), superposition of the metal and graphene lattices of different topology affords various moire superstructures or superlattices. 67,74 The cells of these structures comprise in some cases several thousand atoms.…”