Cleavage Energies of Layered Materials: Bi₁₄Rh₃I₉, Bi₂TeI, β-Bi₄I₄ and 2H-MX₂

In recent years weakly bonded layered systems have become important for the manufacturing of two-dimensional materials. Precise knowledge of the interlayer bonding allows to understand in detail the exfoliation process in these compounds. Cleavage energies are crucial in this respect. Here we report the cleavage energies and electronic properties of the weak topological insulators (TIs) Bi₁₄Rh₃I₉, Bi₂TeI and β-Bi₄I₄, as well as of 2H-transition metal dichalcogenides (MX₂ where M=Mo, W and X=S, Se, Te) determined by means of density functional theory calculations. Our calculations reproduce the experimentally measured value of cleavage energy of graphite, E_c (graphite) = 0.37 Jm⁻², which we use as a benchmark. Based on this, we calculate the cleavage energies of the three weak TIs and 2H-MX₂ systems. We find that all energies are smaller than 2×E_c of graphite. The obtained values suggest the possibility of exfoliation of individual layers in these materials.