Polymerization of nitrogen in sodium azide
Polymerization of nitrogen in sodium azide
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DOI：
10.1063/1.1718250
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发表时间：
2004-06-08
影响因子：
4.4
通讯作者：
Hemley, RJ
中科院分区：
文献类型：
--
作者：
Eremets, MI;Popov, MY;Hemley, RJ
用拉曼光谱、电导、激光加热和剪切形变等方法研究了氮气在NaN3中的高压行为，在120-3300K温度范围内达到160 GPa.叠氮化钠中的氮是类分子形式；叠氮离子N3-是由三个原子以共价键连接的直链，相互作用很弱。通过施加高压，我们大大增强了离子之间的相互作用。我们发现，在19 Gpa以上的压力下，出现了一个新的相，这表明叠氮离子之间存在着强烈的耦合。另一次转变发生在约50 GPa时，伴随着新的拉曼峰的出现和样品的变暗。随着压力的增加，样品在120 Gpa以上变得完全不透明，叠氮化物分子振动消失，证明完成了向具有非晶态结构的非分子氮态的转变，在激光加热到3300K后，非分子氮态结晶。激光加热和剪应力的作用加速了转变，使转变发生在较低的压力下。这些变化可以解释为叠氮离子转变为更大的氮原子团，然后是聚合氮网。聚合体形式在减压时可在钻石顶压室中保留，但在环境条件下可转化回起始叠氮化物和其他新相。(C)2004年美国物理研究所。
The high-pressure behavior of nitrogen in NaN3 was studied to 160 GPa at 120-3300 K using Raman spectroscopy, electrical conductivity, laser heating, and shear deformation methods. Nitrogen in sodium azide is in a molecularlike form; azide ions N3- are straight chains of three atoms linked with covalent bonds and weakly interact with each other. By application of high pressures we strongly increased interaction between ions. We found that at pressures above 19 GPa a new phase appeared, indicating a strong coupling between the azide ions. Another transformation occurs at about 50 GPa, accompanied by the appearance of new Raman peaks and a darkening of the sample. With increasing pressure, the sample becomes completely opaque above 120 GPa, and the azide molecular vibron disappears, evidencing completion of the transformation to a nonmolecular nitrogen state with amorphouslike structure which crystallizes after laser heating up to 3300 K. Laser heating and the application of shear stress accelerates the transformation and causes the transformations to occur at lower pressures. These changes can be interpreted in terms of a transformation of the azide ions to larger nitrogen clusters and then polymeric nitrogen net. The polymeric forms can be preserved on decompression in the diamond anvil cell but transform back to the starting azide and other new phases under ambient conditions. (C) 2004 American Institute of Physics.