超离子H2O冰相的相位过渡动力学由兆赫兹X射线自由电子激光加热实验揭示
R J Husband1, H P Liermann2, J D McHardy3
1Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany. rachel.husband@desy.de.
Nature communications
|September 23, 2024
概括
超离子 (SI) 冰,具有移动质子,有两种形式,其稳定性是有争议的. 这项研究使用超快的X射线加热来显示SI-fcc冰形式仅在~50 GPa以上,影响到行星冰层的理解.
科学领域:
- 高压和高温物理学的高压和高温物理.
- 材料科学是一种材料科学.
- 星球科学 星球科学
背景情况:
- 水 (H2O) 在高压和高温下形成超离子 (SI) 冰相.
- 这些阶段在固体氧子网中具有移动质子.
- SI-bcc和SI-fcc冰的精确稳定场仍在争论中.
研究的目的:
- 用超快X射线技术研究超离子冰相的稳定场.
- 为了澄清SI-bcc和SI-fcc形成的压力-温度条件.
- 了解加热时间尺度和压力-温度路径对SI冰形成的影响.
主要方法:
- 利用来自欧洲X射线自由电子激光器的MHz脉冲列车,用于超快速加热H2O.
- 采用X射线衍射,在动态冷却过程中探测高温状态.
- 在26-69 GPa的压力范围内调查了水样.
主要成果:
- 在加热过程中证实了在26-69GPa范围内向SI-bcc的同结构过渡.
- 观察到的SI-fcc仅在大约50GPa以上,即使有证据表明在较低的压力下化.
- 在较低的压力下,SI-fcc的缺失归因于加热时间短和特定的压力-温度路径.
结论:
- 在实验条件下,SI-fcc的形成仅限于更高的压力 (>50 GPa).
- SI-bcc比SI-fcc更容易从流体相中核化,从而影响观察到的相稳定性.
- 这些发现有助于理解富含冰的行星内部,特别是在动态结事件期间.
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