近日，瑞典斯德哥尔摩大学A. Nilsson团队报道了块体过冷水动态转变的观测。这一研究成果于2025年11月19日发表在《自然—物理学》杂志上。

过冷水中的脆性-强性转变（即弛豫动力学从非阿伦尼乌斯行为转变为阿伦尼乌斯行为）一直被假设用于解释其反常动力学特性。然而，由于体相水在快速结晶前只能被过冷至特定温度，先前关于水体动力学的超快实验研究均未能触及理论预测的转变温度区间，使得该转变始终未被明确证实。

研究组通过结合红外激光泵浦与超短X射线探针技术，系统测量了微米级水滴在飞秒至纳秒时间尺度蒸发冷却过程中的结构弛豫动力学。实验数据在233K附近呈现出动态转变特征：低于该温度时，弛豫动力学偏离简单幂律拟合，转而遵循较平缓的温度依赖性。分子动力学模拟成功复现了上述实验结果。

附：英文原文

Title: Observation of a dynamic transition in bulk supercooled water

Author: Tyburski, R., Shin, M., You, S., Nam, K., Soldemo, M., Girelli, A., Bin, M., Lee, S., Andronis, I., Han, Y., Jeong, S., Oggenfuss, R. A., Mankowsky, R., Babich, D., Liu, X., Zerdane, S., Katayama, T., Lemke, H., Perakis, F., Nilsson, A., Kim, K. H.

Issue&Volume: 2025-11-19

Abstract: The fragile-to-strong transition in supercooled water, where the relaxation dynamics shift from non-Arrhenius to Arrhenius behaviour, has been hypothesized to explain its anomalous dynamic properties. However, this transition remains unresolved, as previous ultrafast experimental studies of bulk water dynamics were limited to temperatures far from the proposed transition due to rapid crystallization. Here we use an infrared laser pump and an ultrashort X-ray probe to measure the structural relaxation in micrometre-sized water droplets, evaporatively cooled at timescales ranging from femtoseconds to nanoseconds. Our experimental data show a dynamic crossover at around 233K. Below this temperature, the relaxation dynamics deviate from simple power-law fits and follow a shallower temperature dependence. Molecular dynamics simulations successfully reproduce our findings.

DOI: 10.1038/s41567-025-03112-3

Source: https://www.nature.com/articles/s41567-025-03112-3