  Density functional theory simulations with conventional (PBE) and hybrid
(HSE06) functionals were performed to investigate the structural and electronic
properties of MXene monolayers, \ce{Ti_{n+1}C_n} and \ce{Ti_{n+1}N_n} ($n$ =
1--9) with surfaces terminated by O, F, H, and OH groups. We find that PBE and
HSE06 give similar results. Without functional groups, MXenes have magnetically
ordered ground states. All the studied materials are metallic except for
\ce{Ti_{2}CO_{2}}, which we predict to be semiconducting. The calculated
density of states at the Fermi level of the thicker MXenes ($n$ $\geqslant$ 5)
is much higher than for thin MXenes, indicating that properties such as
electronic conductivity and surface chemistry will be different. In general,
the carbides and nitrides behave differently with the same functional groups.
