Pressure-stabilized polymerization of nitrogen in manganese nitrides at ambient and high pressures. Issue 9 (22nd February 2022)

• Record Type: Journal Article
• Authors: Niu, Shifeng; Xu, Dan; Li, Haiyan; Yao, Zhen; Liu, Shuang; Zhai, Chunguang; Hu, Kuo; Shi, Xuhan; Wang, Peng; Liu, Bingbing
• Is Part Of: Physical chemistry chemical physics. Volume 24:Issue 9(2022)
• Page Start: 5738
• Page End: 5747
• Publication Date: 2022-02-22
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d1cp03068j
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A systematic high pressure study is performed on Mn–N compounds by using the particle swarm optimization methodology. Abstract : Two stable high-pressure phases ( C 2/ m -MnN4 and P 1̄-MnN4 ) and four metastable phases ( P 4/ mmm -MnN4, P 1̄-MnN5, C 2/ m -MnN6 and P 1̄-MnN8 ) are proposed by using ab initio evolutionary simulations. Besides the reported quasi-diatomic molecule N2, the armchair chain and S-like chain, the N4 ring and N22 ring are firstly reported in the P 4/ mmm -MnN4 and P 1̄-MnN5 phases. A detailed study is performed on the energetic properties, mechanical properties and stability of these polynitrogen structures. Ab initio molecular dynamics simulations show that P 1̄-MnN4 and P 1̄-MnN5 can be quenched down to ambient conditions, and large decomposition energy barriers result in the high decomposition temperatures of P 1̄-MnN4 (2000 K) and P 1̄-MnN5 (3000 K). Interestingly, P 4/ mmm -MnN4 with the N4 ring exhibits outstanding mechanical properties, including high incompressibility, high hardness, uniform strength in the 2-D direction and excellent ductility. Strong N–N covalent bond and weak Mn–N ionic bond interactions are observed in the predicted Mn–N compounds, and the charge transfer between the Mn and N atoms provides an important contribution to the stabilization of polymeric N-structures. All the proposed structures are metallic phases. Our results provide a deep understanding of the chemistry of transition metal polynitrides under pressure and encourage experimental synthesis of these new manganese polynitrides in future.