【摘要】 聚合氮是一种理想的高能密度材料。本工作在室温下将分子氮加压至136 GPa,利用激光加热至2000 K成功合成以共价N-N单键结合的三维网状立方聚合氮cg-N。采用自主设计的高压低温装置,在173 K到300 K的温度范围内测量了cg-N样品的变温拉曼光谱,观察到不同压力下cg-N的A模声子对温度具有不同的响应。基于多声子耦合模型,研究A模频率的蓝移现象和A模声子对温度的响应特性。结果表明低温条件下cg-N拉曼散射效应中三声子耦合过程占主导,133 GPa时的三声子耦合过程对声子模拉曼频移的影响要小于140 GPa,而四声子耦合过程对声子模拉曼频移的影响要大于140 GPa。更多还原

【Abstract】 Polymeric nitrogen is an ideal high energy density material. In this work,molecular nitrogen was compressed to 136 GPa at room temperature,and a three-dimensional network of cubic polymeric nitrogen cg-N bonded by a covalent N-N single bond was successfully synthesized by laser heating to 2000 K. The vibrational properties of cg-N lattices were studied by the temperature-dependence on Raman spectra between 173 K to 300 K using a self-designed high-pressure cryogenic device. It was observed that the A-mode phonons of cg-N had different responses to temperature at different pressures. With the temperature decreasing,the blue-shift and temperature-dependence Raman spectra of the A-mode frequency could be well fitted using a model involing multi-phonon decay processes. Our fitting indicated that the three-phonon decay processes were dominated over the fourphonon ones at low temperatures. The three-phonon decay processes at 133 GPa dominated less than it at 140 GPa,while the four-phonon decay processes at 133 GPa dominated more than it at 140 GPa.更多还原