First-principles study of adsorption of 3d and 4d transition metal atoms on aluminene

Using the first principles calculations based on density functional theory, we study the structural, electronic, and magnetic properties of composite systems of first and second row transition metal (TM) atoms adsorbed aluminene. This study aims to probe the stability of the system as a result of adsorption of TM atoms on the two-dimensional (2D) surface of planar aluminene. We also study the same for two other well-known 2D single-atom-monolayer (SAML) structures, namely, silicene and arsenene, and we compare the results with those of aluminene. The TM atoms are adsorbed on these 2DSAML structures in three different crystallographically inequivalent sites, namely, the hollow (H), the top (T) and the bridge (Br) sites. The stability of the composite systems, which are a combination of a 2D monolayer structure and a TM atom each, is systematically analyzed in terms of binding energy per atom, for eighteen different TM atoms, with 3 d or 4 d electrons in their valence shell. We compare the results of optimized geometry and stability of the above-mentioned 2D structures when the TM atoms are adsorbed at the H, T and Br sites. We further analyze the interaction energy to discuss about and compare the ease of adsorption of various TM atoms on the three different 2DSAML structures. Interestingly, in most of the cases, adsorption of TM atoms typically yields higher interaction energy in case of aluminene when compared with silicene and arsenene systems. Among all the TM adatoms, few atoms have been identified to have higher interaction energy compared to the others. From our calculations of the density of states and band structure of the composite systems, almost all the composite systems have been found to be metallic, except the composite system of Sc atom and silicene, which exhibits a half-metallic state. Further, though all the three 2DSAML structures are non-magnetic in pristine form, a few composite systems are found to be magnetic in nature.