Research on energy, electronic structure, and magnetic changes for compression, sliding, and twisting for 2D Electrides (Y2C, Ca2N) based on the first principle*

Using the first-principles calculations based on density functional theory (DFT), we have studied how the electron structure and total energy change when one of the layers is translated, rotated horizontally (21.8 °), and compressed vertically in the Ca2N and Y2C bilayer, which are representative two-dimensional electride materials. Elctrides show unique phenomena called interstitial anionic electrons (IAEs).
In our study, weak ferromagnetic properties of Y2C have been observed with 0.39 μB per unit cell in the layered structure. For Ca2N (Y2C), the energy barrier of lateral translation was ~20 meV (~120 meV). Interestingly, we found that the twist of the Y2C bilayer gives rise to a change in spin polarization.
We used plane-wave basis sets and the projector augmented wave pseudopotential implemented in the Vienna Ab Initio Simulation Package (VASP). The cut-off kinetic energy was set to 600 eV. The exchange-correlation energy was modeled using the Perdew–Burke–Ernzerhof generalized gradient approximation functional (GGA-PBE). We utilized 15×15×1 k-point grids for the bilayer cell. For the van der walls interaction, Grimme’s DFT-D2 method was used.