Theoretical investigation of the structures, stabilities, and NLO responses of calcium-doped pyridazine: Alkaline-earth-based alkaline salt electrides

Currently, whether alkaline-earth-doped compounds with electride characteristics are novel candidates for high-performance nonlinear optical (NLO) materials is unknown. In this paper, using quantum chemical computations, we show that: when doping calcium atoms into a family of alkaline-substituted pyridazines, alkaline-earth-based alkaline salt electrides M-H3C4N2...Ca(M=H, Li, and K) with distended excess electron clouds are formed. Interestingly, from the triplet to the singlet state, the chemical valence of calcium atom changes from +1 to 0, and the dipole moment direction (mu(0)) of the molecule reverses for each M-H3C4N2...Ca. Changing pyridazine from without (H4C4N2...Ca) to with one alkaline substituent (M-H3C4N2...Ca, M=Li and K), the ground state changes from the triplet to the singlet state. The alkaline earth metal doping effect (electride effect) and alkaline salt effect on the static first hyperpolarizabilities (beta(0)) demonstrates that (1) the beta(0) value is increased approximately 1371-fold from 2 (pyridazine, H4C4N2) to 2745 au (Ca-doped pyridazine, H4C4N2...Ca), (2) the beta(0) value is increased approximately 1146-fold from 2 in pyridazine (H4C4N2) to 2294 au in an Li-substituted pyridazine (Li-H3C4N2), and (3) the beta(0) value is increased 324-(M=Li) and 106-(M=K) fold from 826 (M=Li) and 2294 au (M=K) to 268,679 (M=Li) and 245,878 au (M=K), respectively, from the alkalized pyridazine (M-H3C4N2) to the Ca-doped pyridazine (M-H3C4N2...Ca). These results may provide a new means for designing high-performance NLO materials.(C) 2013 Elsevier Inc. All rights reserved.