High-throughput functionalization of single-layer electride Ca₂N

As a two-dimensional (2D) electride, single-layer Ca₂N is vastly reactive because of its additional electron yet to be passivated. Selecting functionalization species that passivate single-layer Ca₂N is therefore critical for potential applications of this 2D electride at ambient conditions. Here we apply a high-throughput approach of density functional theory calculations to 33 elements across the periodic table for functionalizing single-layer Ca₂N. We compute the adsorption energy for each of these elements adsorped at three different high-symmetry sites of single-layer Ca₂N. The high reactivity of single-layer Ca₂N is reflected by significant adsorption energies for all of the considered species. We also find that the adsorption energy is determined by the interplay of the factors of geometry and electronic structure including the Pauling electronegativity and the Bader charge transfer. In particular, a strong, positive correlation exists between the adsorption energy and the interatomic distance between the adsorbate atom and its nearest-neighboring Ca atom. There is additionally a significant, negative correlation between the adsorption energy and the Pauling electronegativity. By contrast, the negative correlation is much weaker between the adsorption energy and the Bader charge transfer. Finally, we used the cases of oxygen and fluorine atoms adsorped on single-layer Ca₂N as two examples to demonstrate the importance of the three factors. Our work provides a general framework of selecting suitable elements for functionalizing single-layer electrides.