β-RDX单晶的压力诱导相变,The Journal of Physical Chemistry C

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β-RDX单晶的压力诱导相变
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-03-15 , DOI: 10.1021/acs.jpcc.1c00026
Chan Gao ₁ , Junke Wang ₂ , Yang Zhang ₂ , Hao Su ₂ , Zilong Xu ₂ , Rucheng Dai ₁ , Zhongping Wang ₁ , Zengming Zhang _{1,

3}

Affiliation

先前的研究表明，由于结晶质量差，β-RDX容易转变为α-RDX。这阻碍了对β-RDX压力行为的深入了解。在这项工作中，通过高达22 GPa的高压下的拉曼光谱和傅立叶变换红外（FTIR）光谱研究了高质量的β-RDX单晶的相变。根据高压拉曼研究，压力引起的分子变形导致分子对称性降低。β-RDX首先在0.9 GPa附近转变为ε'-RDX，在高温高压下接近ε-RDX。使用密度泛函理论（DFT）方法计算了N–N–C键角，C–C–N–N的二面角以及H–C–H和O–N–O角的变化。这三个CH ₂的不同变化和硝基表示高压下氢键相互作用的变化，而N–N–C键角，C–C–N–N的二面角以及新的N–O和N–N拉伸的变化模式证明了大约6 GPa时β-RDX构象的转化。在进一步的加载压力下，没有观察到进一步的相变行为。但是，压力的增加促进了环的变形。除了CH ₂基团的突变，当释放回环境压力时，β-RDX的所有变化都是可逆的。

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Pressure-Induced Phase Transition of β-RDX Single Crystals

Previous investigations had revealed that β-RDX facilely transforms to α-RDX due to the poor crystalline quality. This hindered obtaining insights into the β-RDX pressure behavior. In this work, phase transition of β-RDX single crystals with high quality was studied via Raman spectra and Fourier transform infrared (FTIR) spectra under high pressures up to 22 GPa. According to high-pressure Raman studies, the pressure-induced molecular deformations resulted in the lowering of the molecular symmetry. β-RDX first transforms to ε′-RDX around 0.9 GPa, close to ε-RDX at high temperature and high pressure. The changes in N–N–C bond angles, the dihedral angles of C–C–N–N as well as the H–C–H and O–N–O angles were calculated using the density functional theory (DFT) method. The different changes in these three CH₂ and nitro groups indicate the variations in hydrogen-bond interactions under high pressure, while the changes in N–N–C bond angles, the dihedral angles of C–C–N–N, and the new N–O and N–N stretching modes prove the transformation of conformation of β-RDX at about 6 GPa. No further phase-transition behavior was observed with further loading pressure; however, the increasing pressure promoted the distortion of the ring. Except for the mutation of CH₂ groups, all of the changes in β-RDX are reversible when released back down to the ambient pressure.

更新日期：2021-03-25

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