在水的分子模型中,超稳定的液体-液体过渡
Jeremy C Palmer1, Fausto Martelli2, Yang Liu3
1Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Nature
|June 20, 2014
概括
研究人员提供了关于超冷水中液态-液态相变的明确证据. 这两种液态之间的过渡,而不是结晶,在特定条件下发生,澄清了水的异常行为.
科学领域:
- 物理化学 物理化学
- 计算材料科学科学 计算材料科学
- 热力学是一种热力学.
背景情况:
- 液态水在冷却到冰点以下时表现出异常的热力学特性,包括增加的压缩性和热容量.
- 理论模型建议在深度超冷水中进行液态-液态相变 (LLPT),但实验验证因冰的快速结晶而受到阻碍.
- 关于水模型中观察到的过渡是否代表真正的LLPT或液晶过渡存在争议.
研究的目的:
- 在深度超冷条件下的ST2水模型中调查液体-液体过渡的存在和性质.
- 在水模拟中提供支持或反对一级LLPT的明确证据.
- 探索分子重组和热力学标准,规范液态水相之间的过渡.
主要方法:
- 采用了六种先进的采样方法来计算ST2水模型的自由能量表面.
- 在过渡过程中分析了协调和拓环结构重排.
- 模拟液体和晶体相之间的热力学可逆路径.
主要成果:
- 确定了两个超稳定的液态相和一个稳定的晶体相在相同的深超冷的热力学条件下共存.
- 证明两个液态相之间的过渡符合第一阶段相位过渡的热力学标准.
- 在ST2模型中观察到两个液态相之间的自由波动,与结晶不同.
结论:
- 在水的ST2模型中提供了第一阶段液态液态过渡的明确证据.
- 该研究解决了关于水模型中过渡的解释的辩论,证实了真正的LLPT.
- 强调了结晶和液体放松之间的时间尺度的分离在使LLPT的观测成为可能方面发挥的关键作用.
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