This article uses first principles to study a single molecular phase of N₂O₄. The structural, electronic, and vibrational properties of N₂O₄ under high pressure are calculated. The a-axis and c-axis compressibilities are basically the same. The bandgap of N₂O₄ decreases as the pressure increases; this is because under the action of pressure, the delocalized electrons in the system increase, so the bandgap decreases. There are two main types of N₂O₄ vibration: telescopic vibration and bending vibration. Herein, the calculated Raman spectrum and infrared (IR) spectrum are compared with the experimental values, and the agreement is better under normal pressure. With the increase of pressure, both the Raman and IR peaks of N₂O₄ appear blueshifted. This is because the applied pressure reduces the volume of the unit cell and reduces the distance between atoms, causing the movement between the atoms to intensify, so the vibration intensity increases. At the same time, under the action of pressure, N₂O₄ increases the IR activity in the high-frequency region and reduces the IR activity in the low-frequency region.

中文翻译：

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N2O4 在压力下的结构、电子和振动特性来自第一性原理研究

本文使用第一性原理研究了N ₂ O ₄的单分子相。_{计算了 N 2} O ₄在高压下的结构、电子和振动特性。a轴和c轴压缩率基本相同。_{N 2} O ₄的带隙随着压力的增加而减小；这是因为在压力作用下，体系中的离域电子增多，因此带隙减小。_{N 2} O ₄有两种主要类型振动：伸缩振动和弯曲振动。将计算得到的拉曼光谱和红外（IR）光谱与实验值进行比较，常压下吻合较好。随着压力的增加，N ₂ O ₄的拉曼和红外峰都出现蓝移。这是因为施加的压力减小了晶胞的体积，减小了原子间的距离，导致原子间的运动加剧，因此振动强度增大。同时，在压力作用下，N ₂ O ₄提高了高频区的IR活性，降低了低频区的IR活性。