Ab initio study on Quasi-Binary Acetonitriletriide Sr3[C2N]2

Abstract

We report using density functional theory (DFT), the ground-state properties of the recently synthesized and characterized Sr3[C2N]2 crystal. The nearly colorless, centrosymmetric Sr3[C2N]2 crystallizes in a monoclinic unit cell with a P21/c space group (No.14) and many of its properties remain unknown basing on the fact that it’s a latecomer in the field. The goal of this study is to fill this information gap through a theoretical prediction. The calculated structural properties were comparable to those obtained by an experimental group led by Clark and co-workers thus giving us extra confidence in the accuracy of our DFT computations on Sr3[C2N]2. We employed the same approach in calculating mechanical and dynamical stabilities together with the electronic density of states of Sr3[C2N]2. No imaginary phonon modes were observed and thus implying dynamical stability. The thirteen elastic constants calculated passed the stability criteria of a monoclinic system. From the computed Poisson’s ratio (η=0.27) and G/B=0.54, our calculations predict Sr3[C2N]2 being brittle and not able to withstand high-pressure applications. To analyze the chemical bonding mechanism, the corresponding total density of states (TDOS) and partial DOS were plotted. The top of the valence band (VB) mainly consists of C 2p states N 2p, N 2s and a slight admixture of Sr 5s states. The bottom of the conduction band (CB) shows a strong hybridization between C 2p, N 2p, N 2s, and Sr 5s states, yielding a bandwidth of 7.18 eV in the entire conduction band. We were able to obtain a tunable electronic gap of 2.65 eV in Sr3[C2N]2. The authors herein note that Sr3[C2N]2 falls in an unknown family of pseudonitrides that may possess novel physical and chemical properties if combined with suitable cations like transition metals. Material scientists are encouraged to scout in this new class of pseudonitrides for future technologies.