高压下主族金属富氮化合物的结构与含能特性

Structure and Energy Properties of Nitrogen-Rich Compounds of Main Group Metals under High Pressure

氮是地球大气的主要成分,体积分数约为78%。在常温常压下,氮以三键的形式(N≡N)结合为稳定的双原子分子。然而,在极端高压的作用下,氮气可以解离成含有双键(N=N)甚至单键(N―N)的固体聚合氮结构。由于N≡N与N=N、N―N之间存在巨大的能量差异,其转变过程中伴随着巨大的能量释放,因此,聚合氮是备受关注的高能量密度物质。然而,单质聚合氮必须在高于百万大气压(100 GPa)的环境下才能实现实验制备,苛刻的合成条件极大地限制了其发展及应用。研究发现,金属元素的引入可降低反应势垒,提供化学压力,有效降低聚合氮的合成压强,并形成丰富多样的聚合氮构型。为此,本文重点介绍了高压下主族金属氮化物的结构和含能特性研究进展,讨论了金属富氮化合物在高压下稳定的物理机制,并对未来新型富氮化合物的设计和制备方向提出展望。

Nitrogen is the main component of the Earth’s atmosphere,accounting for about 78%by volume.At room temperature and pressure,nitrogen is combined into stable diatomic molecules in the form of triple bonds(N≡N).Under the action of extreme high pressure,nitrogen can dissociate into a solid polynitrogen structure containing double bonds(N=N)or even single bonds(N—N).Due to the huge energy difference between N≡N and N=N or N—N,the transformation process is accompanied by huge energy release,so polynitrogen is a high energy density substance that attracts much attention.However,elemental polymerized nitrogen must be prepared in an environment above millions of atmospheric pressure(100 GPa)which is too harsh,greatly limiting the development and application of such materials.Interestingly,the introduction of metal elements can reduce the reaction barrier and provide chemical pressure,which can effectively reduce the synthetic pressure of polynitrogen and form a rich variety of polynitrogen configurations.This paper focuses on the research progress of main group metal nitriding compounds under high pressure,the physical mechanism of stabilities for metal nitrogen-rich compounds under high pressure,and puts forward the prospect of future design and preparation of new nitrogen-rich compounds.