Mechanical properties of 2D ZrC(= 1, 2) MXenes with and without functionalization.

Transition metal carbides and nitrides (MXenes) are considered the new generation of flexible electronic materials because of their superior mechanical strength and flexibility. Based on the density functional theory, the structures, electronic properties and mechanical properties of the 2D Zr-based MXenes with and without surface functional groups (O, F and OH) are investigated systematically to explore their elastic properties and tensile fracture mechanism. The results reveal the tensile strength and critical strain under biaxial tensile direction can reach 52 GPa, 12% for ZrC and 55 GPa, 19% for ZrC, more outstanding than the mechanical behavior of the pristine TiC (47 GPa, 9.5%). The tensile behaviors of the functionalized ZrCT(= 1, 2, T = O, F, OH) strongly depend on the crystallographic orientation and the surface functional group. The phonon spectrum under the critical strain indicates the tensile fracture of the pristine Zr-based MXenes was determined by phonon instability, except along the armchair direction of ZrC and zigzag direction of ZrC. During tensile strain, the collapse of ZrCFand ZrC(OH)(= 1, 2) are mainly caused by internal Zr-C bond rupture and transfer to the surface. While the O-functionalized ZrCO(= 1, 2) presented the opposite collapse trend. Additionally, according to the research results of critical strain, elastic modulus and electrical conductivity, F/OH-terminated ZrC MXene is relatively more suitable for flexible sensors of wearable devices than ZrCT.