Abstract
Recently, two-dimensional (2D) transition metal carbides and nitrides known as MXenes, have gained a lot of attention because of their tunable electronic and magnetic properties depending on surface functionalization. In the present work, the structural, electronic, and magnetic properties of both T and H phases of bare Ti2C and fully surface terminated Ti2 CT2 (T = -F, = O, -OH) are calculated using a set of first principles calculations. The ground state structures of Ti2 CT2 are computed in two and four different configurations for both H and T phases, respectively. We demonstrate that while H phase of Ti2C exhibits half-metallic behavior with magnetic moments of 2 μB per formula unit, it displays metallic behavior with magnetic moments of 1.27 μB , 0.25 ?B per formula unit, and semiconductor behavior with 0.35 eV band gap in -F, -OH, and =O surface functionalization, respectively. We also show that while T phase of Ti2C exhibits metallic behavior with magnetic moment of 1.89 μB per formula unit, it stays in metallic nonmagnetic behavior in both -F and -OH. Meanwhile, it displays semiconductor behavior with 0.25 eV band gap in -O surface functionalization. We expect that our results can advance the future applications of MXenes from energy storage to spintronic.
Highlights
Two-dimensional (2D) freestanding materials show unique properties that differ from those of their conventional bulk (3D) precursors because they lack a degree of freedom
The ground state structure of pristine H phase Ti 2 C is found to be hexagonal crystal structure as shown in Figure 1a. a = b = 3.05 Å are found as equilibrium lattice parameters
We considered two different configurations of functional groups for H phases: functionalized groups stay at the top site of Ti and C atoms shown respectively in Figures 1b and 1c
Summary
Two-dimensional (2D) freestanding materials show unique properties that differ from those of their conventional bulk (3D) precursors because they lack a degree of freedom. Naguib et al reported that they obtained a compose of a few Ti 3 C 2 layers and canonical scrolls produced by exfoliation of Ti 3 AlC 2 in hydrofluoric acid [11] at room temperature These new 2D materials occur when Al atoms are extracted from Ti 3 AlC 2 , which was proposed to be called ”MXene” to emphasize its graphene-like morphology. MXenes has just recently entered the research area as a new member of 2D materials family Their general formula consist of M n+1 AX n (n=1,2,3), M, A, and X represent early transition metal, A-group elements, and C and/or N, respectively. They were produced by selectively etching ”A” layers out of the MAX bulk. After their exfoliation from the MAX phase, MXenes are fully surface-terminated by functionalized groups
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