关键词: superalkaline doped cyclo[18]carbon, structure and electronic properties, nonlinear optical properties, density functional theory (DFT)

Abstract: Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure. Superalkalis have low ionization energy. Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs. In this paper, the geometry, bonding properties, electronic structure, absorption spectrum, and nonlinear optical (NLO) properties of superalkaline $M_{3}$O ($M={\rm Li}$, Na)-doped cyclo[18]carbon were studied by using density functional theory. $M_{3}$O and the C$_{18}$ rings are not coplanar. The C$_{18}$ ring still exhibits alternating long and short bonds. The charge transfer between $M_{3}$O and C$_{18}$ forms stable [$M_{3}$O]$^{+}$[C$_{18}$]$^{-}$ ionic complexes. C$_{18}$$M_{3}$O ($M={\rm Li}$, Na) shows striking optical nonlinearity, i.e., their first- and second-order hyperpolarizability ($\beta_{\rm vec}$ and $\gamma_{\vert \vert }$) increase considerably at $\lambda = 1907$ nm and 1460 nm.

Key words: superalkaline doped cyclo[18]carbon, structure and electronic properties, nonlinear optical properties, density functional theory (DFT)