冰多晶型在液-液临界点附近的熔化曲线
Melting curves of ice polymorphs in the vicinity of the liquid-liquid critical point
AI总结：
本研究利用基于从头算的机器学习模型模拟冰多晶型熔化曲线，发现其均为超临界且不与液-液转变轨迹相交，表明熔化线行为不支持液-液临界点位于冰III和冰V之间的猜想。
摘要：
深过冷水中是否存在液-液临界点一直是一个争论不休的话题，部分原因在于提供确凿的实验证据面临挑战。Mishima 和 Stanley 的开创性工作 [Nature 392, 164 (1998) 和 Phys. Rev. Lett. 85, 334 (2000)] 试图通过研究不同冰多晶型的熔化曲线及其在液-液转变及其相关临界点预期位置附近的亚稳延续来阐明这一问题。基于熔化曲线斜率的连续或不连续变化，Mishima 提出液-液临界点位于冰 III 和冰 V 的熔化曲线之间。在此，我们利用基于从头算量子力学计算的纯预测机器学习模型，通过分子动力学模拟来探索这一猜想。我们使用该模型研究了冰 III、IV、V、VI 和 XIII 的熔化曲线，发现所有被研究的冰多晶型的熔化线都是超临界的，并且不与液-液转变轨迹相交。我们还发现，在跨越液体最大压缩性轨迹时，熔化线斜率发生了显著但连续的变化。最后，我们结合我们的发现对文献进行了批判性分析，得出结论：熔化曲线为超临界的这一情景得到了最新计算和实验证据的支持。因此，尽管绝大多数实验和计算证据与水中存在第二个临界点相一致，但根据我们的计算，冰多晶型熔化线的行为并不能为这一观点提供强有力的支持。
英文摘要：
The possible existence of a liquid-liquid critical point in deeply supercooled water has been a subject of debate in part due to the challenges associated with providing definitive experimental evidence. Pioneering work by Mishima and Stanley [Nature 392, 164 (1998) and Phys. Rev. Lett. 85, 334 (2000)] sought to shed light on this problem by studying the melting curves of different ice polymorphs and their metastable continuation in the vicinity of the expected location of the liquid-liquid transition and its associated critical point. Based on the continuous or discontinuous changes in slope of the melting curves, Mishima suggested that the liquid-liquid critical point lies between the melting curves of ice III and ice V. Here, we explore this conjecture using molecular dynamics simulations with a purely-predictive machine learning model based on ab initio quantum-mechanical calculations. We study the melting curves of ices III, IV, V, VI, and XIII using this model and find that the melting lines of all the studied ice polymorphs are supercritical and do not intersect the liquid-liquid transition locus. We also find a pronounced, yet continuous, change in slope of the melting lines upon crossing of the locus of maximum compressibility of the liquid. Finally, we analyze critically the literature in light of our findings, and conclude that the scenario in which melting curves are supercritical is favored by the most recent computational and experimental evidence. Thus, although the preponderance of experimental and computational evidence is consistent with the existence of a second critical point in water, the behavior of the melting lines of ice polymorphs does not provide strong evidence in support of this viewpoint, according to our calculations.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
