High-throughput computational search for two-dimensional binary compounds: Energetic stability versus synthesizability of three-dimensional counterparts

Using first-principles calculations, the energetic stability of two-dimensional (2D) binary compounds $XY$ is investigated, where $X$ and $Y$ indicate the metallic element from Li to Pb in the periodic table. Here, 1081 compounds in the buckled honeycomb (BHC), buckled square, B2, $\mathrm{L}{1}_0$, and ${\mathrm{B}}_h$ structures are studied. For the compounds that have negative formation energy in the BHC structure or the compounds that can have the ${\mathrm{B}}_h$ structure, the phonon dispersions of the 2D structures are also calculated. We demonstrate that (i) a negative formation energy is neither a sufficient nor necessary condition for yielding the dynamical stability of 2D compounds; and (ii) if a compound in the ${\mathrm{B}}_h$ structure has been synthesized experimentally, that in the BHC structure is dynamically stable.

Figure 1

Schematic illustration for binary compounds in the (a) BHC and (b) BSQ structures. The buckling height is expressed by $\delta$ (total thickness $2\delta$). The primitive lattice vectors are indicated by arrows (red).

Figure 2

The phonon dispersion curves of (a) BSQ LuPt and (b) BHC AuCu.

Figure 3

Plots of $E_j\left(XY\right)$ for 3D structures $j$ as a function of $E_{\mathrm{BHC}}\left(XY\right)$.

Figure 4

The phonon dispersion curves of (a) BHC AlCu and (b) ${\mathrm{B}}_h$ AlSn.