title: A new 2D monolayer BiXene, M2C (M = Mo, Tc, Os).
abstract: The existence of BiXenes, a new family of 2D monolayers, is hereby predicted. Theoretically, BiXenes have 1H symmetry (P6[combining macron]m2) and can be formed from the 4d/5d binary carbides. As the name suggests, they are close relatives of MXenes, which instead have 1T symmetry (P3[combining macron]m1). The newly found BiXenes, as well as some new MXenes, are shown to have formation energies close to that of germanene, which suggests that these materials should be possible to be synthesised. Among them, we illustrate that 1H-Tc2C and 1T-Mo2C are dynamically stable at 0 K, while 1H-Mo2C, 1T-Tc2C, 1H-Os2C, and 1T-Rh2C are likely to be stabilised via strain or temperature. In addition, the nature of the chemical bonding is analysed, emphasizing that the covalency between the transition metal ions and carbon is much stronger in BiXenes than in MXenes. The emergence of BiXenes can not only open up a new era of conducting 2D monolayers, but also provide good candidates for carrier materials aimed at energy storage and spintronic devices that have already been unveiled in MXenes.
authors.affiliation: Department of Physics and Astronomy, Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala, Sweden. sun.weiwei@physics.uu.se igor.dimarco@physics.uu.se.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Sun
authors.affiliation: Department of Earth Sciences, University College London, London WC1E 6BT, UK. yunguo.li@ucl.ac.uk.
authors.forename: Yunguo
authors.initials: Y
authors.lastname: Li
authors.affiliation: China Spallation Neutron Source (CSNS), Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Dongguan 523803, China and Dongguan Institute of Neutron Science (DINS), Dongguan 523808, China.
authors.forename: Baotian
authors.initials: B
authors.lastname: Wang
authors.affiliation: Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian 116024, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Radboud University of Nijmegen, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands and Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Street 19, 620002 Ekaterinburg, Russia.
authors.forename: Mikhail I
authors.initials: MI
authors.lastname: Katsnelson
authors.affiliation: Department of Material Science and Engineering, KTH-Royal Institute of Technology, Stockholm SE-10044, Sweden and Institute of Metal Physics, Ural Division of the Russian Academy of Sciences, 620219 Ekaterinburg, Russia.
authors.forename: Pavel
authors.initials: P
authors.lastname: Korzhavyi
authors.affiliation: Department of Physics and Astronomy, Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala, Sweden. sun.weiwei@physics.uu.se igor.dimarco@physics.uu.se.
authors.forename: Olle
authors.initials: O
authors.lastname: Eriksson
authors.affiliation: Department of Physics and Astronomy, Materials Theory, Uppsala University, Box 516, SE-75120 Uppsala, Sweden. sun.weiwei@physics.uu.se igor.dimarco@physics.uu.se.
authors.forename: Igor
authors.initials: I
authors.lastname: Di Marco