Remarkable nonlinear optical response of excess electron compounds: theoretically designed alkali-doped aziridine M–(C2NH5)n

Abstract

Theoretically designed alkali-doped aziridine M–(C₂NH₅)_n (M = Li, Na and K; n = 1, 2, 3, and 4) are investigated by density functional theory (DFT) and time-dependent TD-DFT. The interaction energies at optimized electronic structures indicate that alkali-doped aziridine are quite stable. The natural population analysis of charges on alkali atoms show that all positive and electronic transitions to LUMO orbitals are large, so that the designed compounds not only have electride features, but also have large flexible ligands. This leads to a high-performance nonlinear optical response (NLO) and this remarkable NLO response mainly comes from alkali atoms. By calculating the first hyperpolarizabilities for M–(C₂NH₅)₄ with M@Calix[4]pyrrole for comparison, we demonstrate that enhancements of the NLO response of M–(C₂NH₅)₄ are 10 to 100 times larger than those of M@Calix[4]pyrrole, and in particular, the largest first hyperpolarizability values of Na–(C₂NH₅)₄ is up to 3.4 × 10⁶ (a.u.).