摘要
在高温高压的极端条件下,分子晶体氮会打破传统三键机制向单键聚合态转变。氮在高压下的独特解离机制使聚合氮的研究意义超越了含能材料范畴,在基础物理学领域亦有深刻的科学意义。继立方偏转聚合氮cg-N(空间群I2_(1)3)之后,第2个在实验上被发现的层状结构聚合氮LP-N(空间群Pba2)一直存在争议。主要的问题在于,LP-N的结构除了没有被高压X射线衍射实验验证之外,还与随后被发现的黑磷结构聚合氮BP-N(空间群Cmca)具有相近的合成温压条件和合成路径以及几乎相同的拉曼光谱特征。LP-N的合成很可能具有独特的相变动力学势垒。为此,选择独辟蹊径,从低温固态分子氮λ-N_(2)出发,利用双面激光加热金刚石压砧技术,结合高压同步辐射X射线衍射和高压拉曼光谱分析方法,在约140 GPa、2600 K的条件下观察到了具有Pba2结构的聚合氮LP-N。结合第一性原理计算,分析了它的原子体积随压力的变化关系(p-V曲线),并探讨了LP-N高温高压合成动力学因素。研究结果不仅使我们更全面地认识LP-N,还进一步揭示了聚合氮的高压路径依赖特性。
Under the extreme conditions of high temperature and high pressure,molecular crystal nitrogen breaks the traditional three-bond mechanism and transforms into a single-bond polymerization state.The unique dissociation mechanism of nitrogen under high pressure makes the research significance of polymeric nitrogen beyond the scope of energetic materials,and also has profound scientific significance in the field of fundamental physics.Following the cubic gauche polymeric nitrogen cg-N(space group I2_(1)3),the second experimentally discovered layered structure polymeric nitrogen LP-N(space group Pba2)has been controversial.The main problem is that,in addition to not being verified by other high-pressure X-ray diffraction experiments,LP-N structure has the similar synthesis temperature and pressure conditions and synthesis pathways,as well as almost the same Raman spectral characteristics as the subsequently discovered black phosphorus structure polymeric nitrogen BP-N(space group Cmca).The high-temperature and highpressure synthesis of LP-N is likely to have a unique phase transition kinetic barrier.In this work,we started from the low-temperature solid-state molecular nitrogen λ-N_(2),used double-sided laser-heated diamond anvil cell(LHDAC)technology,combined with high-pressure X-ray diffraction based on the synchrotron radiation and high-pressure Raman scattering spectroscopy,supplemented by first-principles calculations,and observed the Pba2 structure of polymeric nitrogen LP-N at the conditions of about 141 GPa and about 2600 K.Combined with first-principles calculations,we compared and analyzed its pressure-dependent evolution of the volume per atom(p-V curve)and discussed the kinetic factors of LP-N synthesis at high temperature and high pressure.In addition to a more comprehensive understanding of LP-N,this paper further reveals the high-pressure path-dependent characteristics of polymeric nitrogen.
作者
刘静仪
吴彬彬
陶雨
蒲梅芳
周春银
雷力
LIU Jingyi;WU Binbin;TAO Yu;PU Meifang;ZHOU Chunyin;LEI Li(Institute of Atomic and Molecular Physics,Sichuan University,Chengdu 610065,Sichuan,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201204,China)
出处
《高压物理学报》
CAS
CSCD
北大核心
2024年第4期44-53,共10页
Chinese Journal of High Pressure Physics
基金
国家自然科学基金(12374013,U2030107,11774247)。
关键词
聚合氮
高温高压
路径依赖
X射线衍射
拉曼散射
polymeric nitrogen
high temperature and high pressure
path dependence
X-ray diffraction
Raman scattering
