To assess the performance of our implemented first principles isothermal-isobaric centroid molecular dynamics (CMD) we performed Born-Oppenheimer (BO) CMD simulations in the NPT ensemble for high pressure ices (HPIs) VIII, VII, and X at 270 K. By elevating pressure the crystal system is found to transform from tetragonal to cubic at $\sim$30 GPa, accompanying the proton order (ice VIII)-disorder (ice VII) transition observed to occur in our BO-CMD simulations. Moreover, our simulations are proved to be able to reproduce well both infrared and Raman spectra for HPIs in the frequency range above $\sim 500$ cm⁻¹.

中文翻译：

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高压冰等温等压重心分子动力学模拟的基本原理

为了评估我们实施的第一原理的等温-等压质心分子动力学（CMD）的性能，我们在NPT集合中对270 K的高压冰（HPI）VIII，VII和X进行了Born-Oppenheimer（BO）CMD模拟。升高压力，发现晶体系统从四方晶向立方晶转变为立方晶。$〜$在我们的BO-CMD模拟中观察到30 GPa，伴随着质子有序（冰VIII）-无序（冰VII）的转变。而且，我们的仿真证明能够很好地再现上述频率范围内HPI的红外光谱和拉曼光谱$〜500$ 厘米^-1。