Remarkable electronic and NLO properties of bimetallic superalkali clusters: a DFT study

Excess electron compounds possess remarkable first hyperpolarizabilities (beta(o)) which make them potential candidates for next-generation nonlinear optical materials. Herein, we studied the geometric, thermodynamic, electronic, and nonlinear optical properties of bimetallic superalkali clusters. These clusters are thermodynamically stable with their binding energy per atom ranging from 1.12 to 47.84 kcal mol(-1). The electronic stability and superalkali nature are characterized through calculated ionization energies (IE). Furthermore, the significantly reduced HOMO-LUMO energy gaps reflect excellent properties of bimetallic clusters. The absorption study via TD-DFT shows that these clusters are transparent in the deep UV region of electromagnetic radiations. These excess electron clusters show remarkable hyperpolarizability (beta(o)) values up to 4.3 x 10(4) au. The excess electron causes a significant reduction in excitation energy which results in larger hyperpolarizability values. The obtained first hyperpolarizability is also rationalized by employing the conventional two-level model. The projection of hyperpolarizability on dipole moment (beta(vec)) also agreed with total hyperpolarizability in these clusters which indicated unidirectional charge transfer with dipole moment. Moreover, the studied bimetallic clusters also show larger static second hyperpolarizability (gamma(o)) values up to (6.1 x 10(7) au). We believe that the current study can provide motivation for exploring other excess electron superalkali clusters for NLO applications.