title: Structural stability of polymeric nitrogen: A first-principles investigation.
abstract: The search for the stable single-bonded (polymeric) solid nitrogen attracted much attention in view of its potential application as a high energy density material. In this study, the stability of different candidate polymeric structures of nitrogen has been studied using ab initio calculations based on density-functional theory for the first time, from the angles of thermodynamic stabilities, mechanical stabilities, and dynamical stabilities in the pressure range from 0 to 360 GPa, respectively. According to our results, only Cmcm, A7, rcg, cg, BP, P2(1)2(1)2(1), and Pba2 are competitive structures and more favorable than sc, ch, LB, and cw strcutrues; their stable pressure range were also presented. Among the competitive structures, BP, Pba2, and P2(1)2(1)2(1) are the novel ones for their enthalpies are lower than the cg structure above 170 GPa. We further identify that the P2(1)2(1)2(1) phase can transform to cg structure at pressure below 60 GPa. Also a new phase transition sequence with increasing pressure has been presented, which is from the molecular phase epsilon-N(2) to cg at 47 GPa, to Pba2 at 170 GPa, and then to P2(1)2(1)2(1) at 307 GPa.
authors.affiliation: State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People's Republic of China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.forename: Fubo
authors.initials: F
authors.lastname: Tian
authors.forename: Liancheng
authors.initials: L
authors.lastname: Wang
authors.forename: Tian
authors.initials: T
authors.lastname: Cui
authors.forename: Bingbing
authors.initials: B
authors.lastname: Liu
authors.forename: Guangtian
authors.initials: G
authors.lastname: Zou