A theoretical investigation on doping superalkali for triggering considerable nonlinear optical properties of Si C nanostructure.

In this work, we designed a series of superalkali-doped Si C nanocage M O@Si C (M = Li, Na, K) with donor-acceptor framework. Density functional theory calculations demonstrated that the HOMO-LUMO gap of the complexes conspicuously narrowed with increase of atomic number of the alkali metal, the value decreased from 5.452 eV of pure Si C nanocage to 3.750, 2.984, and 2.634 eV of Li O@Si C , Na O@Si C , and K O@Si C , respectively. This finding shows that the pristine Si C cluster could be transformed to n-type semiconductor by introduction of the superalkali M O. We also showed that the superalkali doping remarkably enhanced the first hyperpolarizability of Si C . Among the studied systems, K O@Si C not only has the narrowest gap but also has the strongest nonlinear optical (NLO) properties, its first hyperpolarizability reached as high as 21695 a.u. The striking results presented in this work will be beneficial for potential applications of the Si C -based nanostructure in the electronic nanodevices and high-performance NLO materials. © 2017 Wiley Periodicals, Inc.