New Cadmium-Nitrogen Compounds at High Pressures.
New Cadmium-Nitrogen Compounds at High Pressures.
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DOI：
10.1021/acs.inorgchem.1c00601
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发表时间：
2021-04
影响因子：
4.6
通讯作者：
Shifeng Niu;Zhihui Li;Hai-yan Li;Xuhan Shi;Z. Yao;Bingbing Liu
中科院分区：
文献类型：
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作者：
Shifeng Niu;Zhihui Li;Hai-yan Li;Xuhan Shi;Z. Yao;Bingbing Liu
采用第一性原理计算方法，结合粒子群优化算法，对CdNx(x=2，3，4，5，6)体系进行了系统的高压研究。我们提出了四个稳定的高压相(P4Mbm-CdN_2，Cmmm-CdN_4，I_4MbM_2d-Cd_4和C_2/c-̅_5)和一个亚稳态高压相(C_2/m-CdN_6)，其结构框架由双原子准分子N_2、标准扶手椅N链、S式弯椅N链、锯齿形反之字形N链和N14网络结构组成。其中，新型的曲折-反曲折N-链和N14网络结构为首次报道。更重要的是，Cmmm-CdN4和C2/m-CdN6在常温下具有很高的稳定性，一旦在高压条件下合成，就可以淬火到常温下。高分解能垒(1.14 eV)导致Cmmm-CdN4的高分解温度(2500K)，而低分解能垒(0.19 eV)导致温和的分解温度(500K)C2/m-CdN6。较高的能量密度和优异的爆炸性能使Cmmm-CdN4、I4̅、C2/c-CdN5和C2/m-CdN6成为潜在的高能材料。电子结构分析表明，所预测的高压结构均为金属相，N-N键和Cd-N键分别为强共价键和离子键。Cd原子的电荷转移对结构的稳定性起着重要的作用。
A systematic high-pressure study of the CdNx (x = 2, 3, 4, 5, and 6) system is performed by using the first-principles calculation method in combination with the particle swarm optimization algorithm. We proposed four stable high-pressure phases (P4mbm-CdN2, Cmmm-CdN4, I4̅2d-CdN4, and C2/c-CdN5) and one metastable high-pressure phase (C2/m-CdN6), for which the structural frames are composed of a diatomic quasi-molecule N2, standard armchair N-chain, S-type bent armchair N-chain, zigzag-antizigzag N-chain, and N14 network structure. Among them, the novel zigzag-antizigzag N-chain and N14 network structure are reported for the first time. More importantly, Cmmm-CdN4 and C2/m-CdN6 possess high stability under ambient conditions, which may be quenched to ambient conditions once they are synthesized at high-pressure conditions. The high decomposition energy barrier (1.14 eV) results in a high decomposition temperature (2500 K) of Cmmm-CdN4, while a low decomposition energy barrier (0.19 eV) results in a mild decomposition temperature (500 K) of C2/m-CdN6. The high energy density and outstanding explosive performance make Cmmm-CdN4, I4̅2d-CdN4, C2/c-CdN5, and C2/m-CdN6 potential high-energy materials. The electronic structure analyses show that these predicted high-pressure structures are all metallic phases, and the N-N and Cd-N bonds are the strong covalent and ionic bond interactions, respectively. The charge transfer from the Cd atom plays an important role in the stability of the proposed structures.