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.