White Thomas G, Griffin Travis D, Haden Daniel, Lee Hae Ja, Galtier Eric, Cunningham Eric, Khaghani Dimitri, Descamps Adrien, Wollenweber Lennart, Armentrout Ben, Convery Carson, Appel Karen, Fletcher Luke B, Goede Sebastian, Hastings J B, Iratcabal Jeremy, McBride Emma E, Molina Jacob, Monaco Giulio, Morrison Landon, Stramel Hunter, Yunus Sameen, Zastrau Ulf, Glenzer Siegfried H, Gregori Gianluca, Gericke Dirk O, Nagler Bob
Department of Physics, University of Nevada, Reno, NV, USA.
SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
Nature. 2025 Jul;643(8073):950-954. doi: 10.1038/s41586-025-09253-y. Epub 2025 Jul 23.
In their landmark study, Fecht and Johnson unveiled a phenomenon that they termed the 'entropy catastrophe', a critical point where the entropy of superheated crystals equates to that of their liquid counterparts. This point marks the uppermost stability boundary for solids at temperatures typically around three times their melting point. Despite the theoretical prediction of this ultimate stability threshold, its practical exploration has been prevented by numerous intermediate destabilizing events, colloquially known as a hierarchy of catastrophes, which occur at far lower temperatures. Here we experimentally test this limit under ultrafast heating conditions, directly tracking the lattice temperature by using high-resolution inelastic X-ray scattering. Our gold samples are heated to temperatures over 14 times their melting point while retaining their crystalline structure, far surpassing the predicted threshold and suggesting a substantially higher or potentially no limit for superheating. We point to the inability of our samples to expand on these very short timescales as an important difference from previous estimates. These observations provide insights into the dynamics of melting under extreme conditions.
在他们具有里程碑意义的研究中，费希特和约翰逊揭示了一种他们称之为“熵灾变”的现象，即过热晶体的熵与其液态对应物的熵相等的临界点。这一点标志着固体在通常约为其熔点三倍的温度下的最高稳定性边界。尽管有对这个最终稳定性阈值的理论预测，但由于许多中间失稳事件（俗称一系列灾变）在远低于该温度时就会发生，其实际探索受到了阻碍。在这里，我们在超快加热条件下通过实验测试这个极限，利用高分辨率非弹性X射线散射直接跟踪晶格温度。我们的金样品被加热到超过其熔点14倍的温度，同时保持其晶体结构，远远超过了预测阈值，这表明过热的极限可能更高，甚至可能没有极限。我们指出，我们的样品在这些非常短的时间尺度上无法膨胀，这是与先前估计的一个重要差异。这些观察结果为极端条件下的熔化动力学提供了见解。
