title: Diverse ruthenium nitrides stabilized under pressure: a theoretical prediction.
abstract: First-principles calculations were performed to understand the structural stability, synthesis routes, mechanical and electronic properties of diverse ruthenium nitrides. RuN with a new I-4m2 symmetry stabilized by pressure is found to be energetically preferred over the experimental NaCl-type and ZnS-type ones. The Pnnm-RuN2 is found to be stable above 1.1 GPa, in agreement with the experimental results. Specifically, new stoichiometries like RuN3 and RuN4 are proposed firstly to be thermodynamically stable, and the dynamical and mechanical stabilities of the newly predicted structures have been verified by checking their phonon spectra and elastic constants. A phase transition from P4/mmm-RuN4 to C2/c-RuN4 is also uncovered at 23.0 GPa. Drawn from bonding and band structure analysis, P4/mmm-RuN4 exhibits semi-metal-like behavior and becomes a semiconductor for the high-pressure C2/c-RuN4 phase. Meanwhile the P21/c-RuN3 shows metallic feature. Highly directional covalent N-N and Ru-N bonds are formed and dominating in N-enriched Ru nitrides, making them promising hard materials.
authors.affiliation: Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Yunkun
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Lailei
authors.initials: L
authors.lastname: Wu
authors.affiliation: Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, China.|Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Wan
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
authors.forename: Yangzheng
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.|Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Hu
authors.affiliation: Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Gao
authors.affiliation: Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Li
authors.affiliation: Key Laboratory of Metastable Materials Science and Technology, College of Material Science and Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Jingwu
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.|Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
authors.forename: Huiyang
authors.initials: H
authors.lastname: Gou