  Electride materials offer attractive physical properties due to their loosely
bound electrons. Ca2N, an electride in the two-dimensional (2D) form was
successfully recently synthesized. We conducted extensive first-principles
calculations to explore the mechanical, electronic, optical and transport
response of single-layer and free-standing Ca2N and Sr2N electrides to external
strain. We show that Ca2N and Sr2N sheets present isotropic elastic properties
with positive Poisson's ratios, however, they yield around 50% higher tensile
strength along the zigzag direction as compared with armchair. We also showed
that the strain has negligible effect on the conductivity of the materials; the
current in the system reduces by less than 32% for the structure under ultimate
uniaxial strain along the armchair direction. Compressive strain always
increases the electronic transport in the systems due to stronger overlap of
the atomic orbitals. Our results show that the optical spectra are anisotropic
for light polarization parallel and perpendicular to the plane. Interband
transition contributions along in-plane polarization are not negligible, by
considering this effect the optical properties of Ca2N and Sr2N sheets in the
low frequency regime significantly changed. The insight provided by this study
can be useful for the future application of Ca2N and Sr2N in nanodevices.
