Nearly flat bands and ferromagnetism in the terminated Mn2C MXene

Mn2C MXene functionalized by oxygen is a semiconducting antiferromagnet and an efficient visible light absorber

“…These results agree well with recent theoretical studies showing ground-state spin configuration equivalent to our T1-AFM1. 25,45 On the other hand, predicted ferromagnetic ground-state and conducting antiferromagnetic states in other studies 24 can be the result of a limited search at the PBE level with different geometries. Interestingly, our original 1 × 1 unit cell conformers (T1-FM0, T1-AFM0, and H1-AFM0) are the lowest ones in Table 1, implying that the investigation of only the unit cell of Mn 2 CO 2 is leading to biased knowledge: ferromagnetic solution (H1-FM0) would be the false ground state with a much smaller band gap than T1-AFM1.…”

“…The Mn-based MXenes show potential because of the broad palette of their magnetic phases, and the parent MAX phase was already prepared (Mn 2 GaC). 18,20,21 Typical calculations from basic (GGA) density functional theory (DFT) indicated the conducting behavior of Mn 2 CO 2 , 14,24 while recent studies predicted it was also semiconducting. 5,25–27,45 To reconcile such uncertainties, we systematically generated a large set of Mn 2 CO 2 magnetic solutions using meta -GGA density functional SCAN and hybrid density functional HSE06, proving that all conformers embody the semiconducting behavior (while the band gap varied).…”

“…Also, other Mn-containing magnetic MAX phases such as (Cr,Mn) 2 AlC or (Mo,Mn) 2 GaC were prepared. 22,23 Mn-based MXenes are typically predicted as conductors 14,24 and the standard prediction tool for materials modeling, density functional theory (DFT), is robust and generally accepted. However, DFT can sometimes predict different or opposite properties when using its various levels of implementation (mainly various density functionals) for complicated systems ( e.g.…”