title: Theoretical investigation of planar square carbon allotrope and its hydrogenation.
abstract: Using density functional theory we investigate a novel carbon allotrope 'SqC': a square planar material that can be more than tetracoordinated. Carbon atoms in this 2D square Bravais lattice form an unusual five-center four-electron bond with neighboring four carbon atoms (tetracoordination). Such an electron-deficient bonding leaves an empty orbital which enables penta- or hexa-coordinated carbon atom. Indeed, our simulations demonstrate such penta- and hexa-coordinated configurations upon partial and complete hydrogenation, respectively. Surprisingly, in all the forms SqC shows the metallic character. SqC has the binding energy of 6.7 eV and it also satisfies the Born stability criteria. Yet our phonon calculations show that it may only be considered as quasi-stable.
authors.affiliation: Department of Mechanical Engineering, University of Alberta, Edmonton, AB, T6G 2G8, Canada. pujari@ualberta.ca
authors.forename: Bhalchandra S
authors.initials: BS
authors.lastname: Pujari
authors.forename: Andrey
authors.initials: A
authors.lastname: Tokarev
authors.forename: Deepashri A
authors.initials: DA
authors.lastname: Saraf
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002621:Chemistry / Q000379:methods; D002627:Chemistry, Physical / Q000379:methods; D004563:Electrochemistry / Q000379:methods; D004581:Electronics; D004583:Electrons; D006108:Graphite / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D012984:Software
chemical_list: D008670:Metals; D002244:Carbon; D006108:Graphite; D006859:Hydrogen