First‐principles investigation of elastic and electronic properties of double transition metal carbide MXenes

Abstract

We use first‐principles‐based density functional theory (DFT) calculations to investigate the structural, elastic, and electronic properties of various pristine and oxygen (O)‐functionalized double transition metal (DTM) MXenes with general formulas of M2′M′′C2 and M2′M′′C2O2, where M′ = Mo, Cr and M′′ = Ti, V, Nb, Ta. The dynamic stability of the DTM MXenes are assessed and elastic stiffness constants (Cij) are used to investigate the mechanical stability and properties of the compositions. The calculated elastic properties of the pristine Mo‐based MXenes are found to be superior compared to Cr‐based compounds. Furthermore, the O‐functionalized MXenes exhibit improved in‐plane elastic constants, Young's moduli, and shear moduli compared to their pristine counterpart. We observe that the hybridization of the energy states results in stronger covalent interactions as such increased elastic properties for the M2′M′′C2O2 MXenes. Ashby plot clearly demonstrates superior materials properties of O‐functionalized Mo‐based DTM MXenes compared to other commonly known two‐dimensional materials. All the MXenes exhibit metallic character evident from the density of states (DOS) calculations. Additionally, the work functions are studied and the calculated values are higher in the case of O‐functionalized MXenes. Overall, this work will be a guide for future investigations on the mechanical properties of DTM MXenes for their targeted applications in structural nanocomposites.

Influence of vacancies on the optical and electronic properties of the rhombohedral In2O3 oxide

“…In addition, the total energy of In 2 O 3 with these vacancies was treated by the density mixing scheme in conjunction with the conjugate gradient technique. During the structural optimization, the lattice parameters and atomic positions of In 2 O 3 with these vacancies were fully relaxed 33–36 …”

“…During the structural optimization, the lattice parameters and atomic positions of In 2 O 3 with these vacancies were fully relaxed. [33][34][35][36] 3 RESULTS AND DISCUSSIONS…”

Recent progress in MXenes-based lithium-sulfur batteries

“…Meanwhile, in most MXenes, the p-band of carbon/nitrogen is lower than the d-band of transition metals. It is observed that in all the functionalized MXenes discussed, due to higher electronegativity of X (C and N) atoms and connected functional groups compared to transition metals, transition metals become positively charged by losing electrons [30] . Additionally, the electronic properties of monolayer Ti 3 C 2 X 2 (X = F, Cl, Br, I) functionalized with halogen atoms have also been studied.…”

“…In addition to the structural properties, MXenes also possess other important properties, with metal conductivity being the most significant. All the MXenes exhibit metallic properties without any surface functionalization [30,31] . However, after surface terminal modification, Sc 2 CF 2 , Sc 2 C(OH) 2 , Sc 2 CO 2 , Ti 2 CO 2 , Zr 2 CO 2 , and Hf 2 CO 2 become semiconductors with a bandgap of approximately 0.25-2.0 eV.…”

Machine Learning Enabled Prediction of High Stiffness 2D Materials

“…As seen in Figure a, oxygen functionalized MXenes such as W 3 N 2 O 2 H 2 and Ta 4 C 3 O 2 have higher 2D-stiffness than bare MXenes, W 3 C 2 and Ta 4 C 3 . The strong M–O bond formed due to oxygen functionalization is responsible for the higher 2D-stiffness of oxygen functionalized MXenes. − However, as seen in Figure b, the 3D-stiffness of oxygen functionalized and bare MXenes are comparable. In general, MXenes exhibit higher 2D-stiffness than all other classes of 2D materials.…”