Ab-initio calculations of chemical and optoelectronic properties of 7-atom Pt-Y [Y = Li, Na, K]

Using density functional theory, we investigated structural, chemical, electronic, and optical properties of the 7 neutral atom Pt-Y [Y = Li, Na, K] pure and nanoalloys. The generalized gradient approximation and ultrasoft pseudopotential are considered. Interesting results are achieved. In particular, Pt₆Li cluster shows a higher absolute value of the binding energy (BE) whereas in all other Pt_7-mY_m systems, this value decreases when m increases. The more the atomic radius increases, the less the resulting alkali metal nanoclusters are cohesive. The most stable structure of Pt_7-mY_m cluster is obtained when m = 4 for Li and Na atoms, whereas for K atom, this occurs for m = 3. Moreover, the calculated absorption spectra of the Pt_7-mY_m (m = 2, 4, 6) have revealed that the doping with Li, Na, and K widens the absorption band. Also, the absorption spectra obtained are more pronounced in the low energy zone. It appears that the electron absorption strength is high in low excitation energy zone. On the other hand, the nanoclusters with m = 1, 3, 5, 7 (odd numbers of electrons) showed metallic character with absorption spectra that could not be easily guessed through the present numerical calculations. The nanoclusters Pt_7-mY_m with even numbers of dopant atoms showed semiconductor properties with the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap increasing as the number of doping atoms increases.