Investigation of van der Waals interactions in two-dimensional MXenes via first-principles simulations

This study systematically examines van der Waals (vdW) interactions in MXenes using density functional theory (DFT) with dispersion-corrected methods. We evaluate Grimme D2, Grimme D3, the exchange-hole dipole moment (XDM) method, and the nonlocal vdW-DF2 functional, pointing out their impact on interlayer distance, lattice parameters, and in-plane elastic stiffness for ten M₂CX_T compositions (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W and X = O, F, H, and OH). Interlayer spacings range from 4.8 to 9.7 Å, lattice constants range from 2.9 to 3.3 Å, and corrected in-plane stiffness values range from ∼100 to 360 N m^-1. Oxygen terminations tend to produce the highest stiffness, while hydrogen terminations provide denser lattices and relatively strong stiffness, making them promising for both mechanically resilient and flexible devices. Fluorine and hydroxyl groups provide increased spacings and softer responses, offering additional tunability. Metal-dependent trends describe bond contraction across a period and relativistic effects down a group. Benchmark comparisons suggest that D3 and XDM most closely reproduce experimental ranges (e.g., Ti₃C₂T_x XRD and nanoindentation), but D2 overbinds and vdW-DF2 underbinds. No correction is superior in all cases; method choice must be guided by the properties and chemistry of interest. This reproducible dataset establishes the structure-property tendencies between metals, terminations, and vdW schemes, providing design rules for the engineering of MXenes in flexible electronics, energy storage, and catalysis.