  We report using density functional theory (DFT), the ground-state properties
of the recently synthesized and characterized Sr$_3$[C$_2$N]$_2$ crystal. The
nearly colorless, centrosymmetric Sr$_3$[C$_2$N]$_2$ crystallizes in a
monoclinic unit cell with a $P2_1/c$ 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
Sr$_3$[C$_2$N]$_2$. We employed the same approach in calculating mechanical and
dynamical stabilities together with the electronic density of states of
Sr$_3$[C$_2$N]$_2$. 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
($\eta$=0.27) and G/B=0.54, our calculations predict Sr$_3$[C$_2$N]$_2$ 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
Sr$_3$[C$_2$N]$_2$. The authors herein note that Sr$_3$[C$_2$N]$_2$ falls in an
unknown family of pseudonitrides that may possess novel physical and chemical
properties.
