内容来源：https://www.quantamagazine.org/physicists-discover-the-most-complex-forms-of-ice-yet-20260427/

内容总结：

物理学家发现迄今最复杂冰形态

引言

冰的形态远不止冰箱或冰川中的那种。自1900年以来，科学家已观测到20多种冰相，其中许多在极端条件下形成。这个不断增长的名单包括热冰，甚至能导电的冰。

冰的多样性与新发现

冰是指任何固态且结晶态的水形态，即具有重复分子结构。过去十年，计算机模拟预测了数万种可能的冰形态。尽管在地球上罕见，但奇异冰可能存在于地外环境中，从寒冷的无定形彗尾到炽热高压的冰行星核心。

随着实验技术进步，物理学家不断发现惊喜。加利福尼亚州劳伦斯利弗莫尔国家实验室（LLNL）研究科学家马里乌斯·米洛表示：“你取水，仅凭压缩方式——稍快、稍慢、上下施压，在合适的时间尺度——就能发现完全意想不到的行为。”

通过摒弃旧假设并应用新技术，科学家在过去一年发现了三种新冰，包括有史以来最复杂的两种冰相。剑桥大学物理学家克里斯·皮卡德说：“这似乎是一个非凡的时刻，他们确实发现了更多这类结构。”

最新发现：冰XXI与冰XXII

2018年，韩国标准与科学研究院（KRISS）博士后研究员金容在对室温水在极端压力下结冰的实验数据进行分析时，注意到一个短暂异常现象：冰似乎先失去结构，然后在过渡到下一相前变成分子混乱状态。2025年，KRISS团队使用改进实验成功重现了这一奇特结构——其复杂性最初看似随机，但宏观上具有周期性。

研究团队利用德国欧洲X射线自由电子激光装置的高功率X射线激光束照射冰样，测量散射情况。大多数冰相只会将光线反射到几个不同方向，但这个样本沿约15条不同路径反射光线。分析后，该晶体模式中的分子数量高达152个，该冰相被正式命名为“冰XXI”。

更令人惊讶的是，所有已预测的数万种冰相中均未找到匹配项。皮卡德表示：“他们发现的东西比我们预测的复杂得多。”与此同时，冈山大学团队在2018年的更窄范围模拟中实际上已预测了该结构，还预测了另外两种尚未发现的冰相。

进一步突破：冰XXII与冰IV

东京大学小林弘树领导的团队重现冰XXI的过程中，发现了邻近的“冰XXII”——更为复杂，每304个分子才重复一次分子模式。在更低温度下，该团队还找到可靠生产“冰IV”的方法，这是一种非常难以捕捉的亚稳态冰相，素有“鬼火”之称。

塑料冰VII的发现

2025年，洛桑联邦理工学院利维亚·博韦团队在《自然》杂志发表论文，报告首次观察到“塑料冰VII”。这是冰VII的高压变体，当冰被加热到约500摄氏度时出现。在这种形态中，水分子保持固态晶体结构，但会快速原地旋转。

塑料冰VII的旋转分子赋予冰一定的弹性，被认为存在于冰冷卫星核心内部，是冰在变成“超离子冰”（2019年首次发现）前的中间状态。在超离子冰中，氢原子完全脱离与氧原子的键合，使冰能导电。

科学意义与应用前景

金容的样品并未直接跳至最稳定状态，而是从水先变成冰XXI，再变成冰VII。这些中间相被称为亚稳态，证明某些相变是分步而非一次性完成的。

这些发现支持了奥斯特瓦尔德阶梯规则理论：系统会过渡到最近且最容易达到的相态，而非热力学上最稳定的状态——有时还会“卡住”。皮卡德解释：“有时最容易形成的状态恰恰是最不稳定的。”

观察到更多亚稳态正在积累证据，证明这一理论不仅适用于冰，也适用于其他晶体，包括药物晶体。改变药物的相态会影响其疗效，奥斯特瓦尔德理论有助于预测何时可能发生这种情况。

科学家目前正致力于开发新方法，以提高可施加在水上的压力。科帕里说：“我们目标的最终压力非常高，是地球中心压力的两倍以上。”米洛总结道：“我们生活在水星球上，却仍在了解水的能力。我们观察得越多，实验做得越好，发现的惊喜就越多。”

中文翻译：

物理学家发现迄今最复杂冰形态
引言
冰的形态远比你在冰柜或冰川中见到的要丰富。自1900年以来，科学家已观测到20多种冰相，其中许多是在极端条件下形成的。这份不断增长的清单包括热冰，甚至还有导电的冰。
冰是指任何固态且呈结晶形态的水相，这意味着其分子结构具有重复性。过去十年间，计算机模拟预测了数万种可能的冰形态。虽然这些奇特的冰在地球上并不常见，但它们可能存在于地球之外的环境中——从寒冷无定形的彗尾到炽热高压的冰态行星核心。
随着物理学家通过改进实验技术对水进行测试，他们不断发现惊喜。"你拿水，只需改变压缩方式——稍快一点、稍慢一点、上下施压，在恰当的时间尺度内——就能发现这种完全出乎意料的行为，"加利福尼亚州劳伦斯利弗莫尔国家实验室的研究科学家马里乌斯·米洛表示。
摒弃旧有假设并应用新技术后，科学家在过去一年内发现了三种新型冰，其中包括迄今所见最复杂的两种冰相。"眼下似乎是个非凡的时期，"剑桥大学物理学家克里斯·皮卡德说，"他们确实发现了更多这样的结构。"
空间异形
水的形状使其极具多变性。其分子结构可以组装成多种可能的构型。
每个水分子就像一个中心单元，带有四条因电磁力而展开的"手臂"。中心单元是一个氧原子，与其键合的是两个氢原子，另外像额外肢体般伸出的则是两对剩余自由电子。
在最常见的冰形态中，这些构建单元组合成笼状六边形结构。这种排列的松散性使得普通冰的密度低于液态水。这就是冰能漂浮、水体自上而下结冰的原因，从而让水下生物得以越冬。
然而，对水施加压力后，其形状可以压缩并重叠，形成看似无穷无尽的可能图案。由于能呈现如此多不同形态，"水的物理和化学性质在不同环境中可能截然不同，"洛桑联邦理工学院物理学家莉维娅·博韦说，"这在拓扑结构上非常优美。"
2018年，一个来自欧洲和日本的国际研究小组创建了一个雄心勃勃的水分子动力学计算机模拟，旨在预测尚未发现的冰形态。结果生成了一个包含超过7.5万种冰相的目录，每种冰相的特征在于水分子在不同温度和压力组合下能够略微不同的方式排列。
现实中，科学家并不期望发现接近那么多冰相；仅仅因为一种结构在数学上可能存在，并不意味着它会在自然界中形成。"当新相的存在仅基于模拟时，这类说法总是存在一些不确定性，"劳伦斯利弗莫尔国家实验室物理学家费代里卡·科帕里在电子邮件中写道。
有些冰相的形成需要极其巨大的能量，其他一些则脆弱到会立即崩塌。科学家试图将预测范围缩小到那些看似可行的冰相。"最终会过滤到更少的几种，"参与模拟工作的皮卡德说，"但现实是，我们并不确切知道该如何设置这个过滤器。"
为了发现冰实际存在的形态，科学家们走进了实验室。
压力之下
2018年，金勇宰是韩国标准与科学研究院的博士后，研究室温下的水如何在极端压力下结冰。实验涉及将一滴水夹在两颗钻石之间，并通过高速成像和其他分析技术研究其变化的分子结构。
在分析实验数据时，金勇宰注意到了起初看似错误的现象。在短短几十毫秒内，冰似乎失去了结构，在过渡到下一相之前分解成一团混乱的分子。金勇宰担心汗水或污垢污染了水。"在那个阶段，我感到更多的是焦虑而不是兴奋，"他说。他将这一观察结果分享给了团队其他成员，但没有时间继续跟进。
2025年，韩国标准与科学研究院的研究人员使用金勇宰的钻石装置进行了改进版的相同实验，并成功重现了这种奇特结构。它如此复杂，以至于最初看起来几乎是随机的。"但退后一步，"金勇宰说，"我们从宏观上观察这种结构，发现它具有周期性。"
研究人员将他们的装置带到了德国的欧洲X射线自由电子激光设施，那里有一台激光器，通过3.4公里长的隧道加速电子，然后让电子穿过特殊磁铁，产生X射线脉冲。"X射线光束越强，你得到的晶体结构图像就越清晰，"皮卡德说。
科学家让高功率X射线激光束穿过冰，并测量光束的散射情况。大多数冰相只会让射线沿少数几个不同方向反弹，因为它们的晶体图案在几个分子后就重复了。但这次样品使光线沿着大约15条不同路径传播。当科学家分析图像时，晶体图案中的分子数量达到了惊人的152个。该团队对这种结构的观察为这种冰相赋予了正式的罗马数字名称——冰XXI。
更重要的是，这种新相完全出乎意料。团队仔细搜寻了皮卡德小组预测的数万种冰相以寻找匹配项，但一无所获。原来，冰XXI的重复结构超出了模拟搜索范围的大小。"他们基本上发现了比我们预测的复杂得多的东西，"皮卡德说。
韩国标准与科学研究院团队不知道的是，冈山大学的一个小组实际上在同样于2018年创建的另一个更窄范围的模拟中预测了这种结构。这个更聚焦的模拟还预测了另外两种尚未发现的冰相。
变化
韩国标准与科学研究院的研究人员以及如今在劳伦斯利弗莫尔国家实验室的金勇宰，起初并非为了发现新的冰相。相反，他们想研究水的另一个奇特性质，即与水相变相关的问题。经典相变理论预测，任何系统都会回到其最低能量状态。但水并不总是遵循预测。
例如，金勇宰的样品在被钻石装置挤压时，并没有直接跃迁到其最稳定的状态（在该压力水平下，这种状态是一种称为冰VI的形态）。相反，它从水跃迁到冰XXI，再到冰VII。这些中间相被称为亚稳态，它们的存在表明某些相变是分步发生，而非一次性完成的。
水的亚稳态支持一种称为奥斯特瓦尔德分步规则的相变理论，该理论以德国物理化学家、阿尔伯特·爱因斯坦的同侪威廉·奥斯特瓦尔德命名（爱因斯坦最初申请奥斯特瓦尔德实验室的工作时被拒，但两人后来成为朋友，奥斯特瓦尔德最终提名爱因斯坦获得诺贝尔奖）。奥斯特瓦尔德分步规则表明，系统会过渡到最近且最容易达到的相态，而非热力学上最稳定的相态——并且有时会卡在其中。"这真是一个自相矛盾的有趣现象：有时最容易形成的状态恰恰是最不稳定的，"皮卡德说。
由东京大学的Hiroki Kobayashi领导的小组已经跟进冰XXI的发现（如预印本文章所述），使用不同技术重现了该冰相。在此过程中，他们发现了一个邻近的冰相——现在称为冰XXII——它更加复杂，每304个分子才重复一次图案。
在较低温度下，该小组还找到了一种可靠生产冰IV的方法。冰IV是一种亚稳态冰相，如此难以捉摸，以至于赢得了"鬼火"的绰号，源自民间传说中引诱旅人的幽灵之光。
随着科学家观测到更多亚稳态，他们正在收集证据，证明奥斯特瓦尔德理论的这种应用准确地描述了相变如何运作——不仅在冰中，在其他类型的晶体中也是如此，包括用于药物中的晶体。改变药物的相态会改变其药效，这是工厂需要防范的。"有时药物会从一种相态转变为另一种，然后毁掉整批产品，"皮卡德说。奥斯特瓦尔德的理论有助于预测这种情况何时会发生。
让我们旋转起来
2025年，博韦在洛桑的团队发现了一种更小但某些方面更奇特的亚稳态冰相。在《自然》杂志发表的一项研究中，他们报告了首次观测到塑性冰VII。这是冰VII（一种高压冰相）的变体，当冰被加热到约500摄氏度时会出现。
在塑性冰中，水分子保持其固态晶体结构，但在原地快速旋转。这种运动很难观测；氢对X射线几乎不可见，而在水分子中，X射线只会被氧原子偏转。"如果你看不到氢原子，就无法真正判断水分子是否在旋转，"皮卡德说。
因此，除了使用X射线，博韦的团队还采用了另一种技术：他们将中子流射入热冰中。"那些中子技术非常强大，"米洛说，"你可以观察分子，看它们是否振动、是否旋转、是否既振动又旋转。"
塑性冰VII中旋转的分子赋予了冰一定的弹性，就像一张轻柔的蹦床。据信，塑性冰VII存在于冰冷卫星的核心中，并且被认为是冰在转变为更热形态（称为超离子冰，即冰XVIII，于2019年首次发现）之前所经历的中间状态。在这种形态中，氢原子完全摆脱了与氧原子的键合，使冰能够导电。
像博韦这样的研究表明，观测更多水相可能需要使用新的实验技术或结合多种不同技术。科学家目前正在研究新方法，以提高能施加到水上的压力。"我们最终的目标压力非常高，"科帕里说，"是地球中心压力的两倍以上。"
我们生活在水行星上，但我们仍在了解水的能力。"我们观察得越多，实验越精良，发现的惊喜就越多，"米洛说。

英文来源：

Physicists Discover the Most Complex Forms of Ice Yet
Introduction
Ice comes in more forms than what you’ll find in a freezer or a glacier. Since 1900, scientists have observed more than 20 phases of ice, many of them shaped under extreme conditions. The growing list includes hot ice and even ice that conducts electricity.
Ice is the name for any phase of water that is solid and crystalline, meaning that it has a repeating molecular structure. Over the past decade, computer simulations have predicted tens of thousands of possible forms of ice. Though uncommon on our planet, exotic ice may exist in off-Earth environments, from cold and amorphous comet tails to the hot and crushing cores of icy planets.
As physicists put water to the test with improved experimental techniques, they keep finding surprises. “You take water, and just the way you compress it — a little bit faster, a bit slower, up and down, at the right timescale — and then you can find this completely unexpected behavior,” said Marius Millot, a research scientist at Lawrence Livermore National Laboratory (LLNL) in California.
Abandoning old assumptions and applying new techniques, scientists have discovered three new kinds of ice in the past year, including two of the most complex ice phases ever seen. “It seems a remarkable time at the moment,” said Chris Pickard, a physicist at the University of Cambridge. “They’re really finding a lot more of these structures.”
Space Oddity
The shape of water makes it exceptionally versatile. Its molecular structure can assemble in many possible configurations.
Each water molecule looks like a central unit with four arms spread apart by the electromagnetic force. The central unit is an oxygen atom. Bonded to it are two hydrogen atoms, and sticking out like extra limbs are two pairs of leftover free electrons.
In the most common form of ice, these building blocks combine to form a cagelike hexagonal structure. The spaciousness of this arrangement makes typical ice less dense than liquid water. This is why ice floats, and why bodies of water freeze from the top down, allowing underwater life to survive the winter.
Put water under pressure, though, and its shape can compress and overlap in a seemingly endless bounty of possible patterns. Because it can take so many different forms, “the physics and the chemistry of water can be completely different” from one environment to the next, said Livia Bove, a physicist at the Swiss Federal Institute of Technology Lausanne. “It’s topologically beautiful.”
In 2018, an international research group from Europe and Japan created an ambitious computer simulation of the dynamics of water molecules that aimed to predict undiscovered forms of ice. The result was a catalog of over 75,000 phases, each characterized by a slightly different way that the water molecules could fit together when subjected to a different combination of temperature and pressure.
In reality, scientists don’t expect to find anywhere near that many phases; just because a structure is mathematically possible does not mean that it will form in nature. “There is always a bit of uncertainty associated with claims of the existence of new phases when they are solely based on simulations,” wrote Federica Coppari, a physicist at LLNL, in an email.
Some phases would require a ridiculous amount of energy to form. Others are so fragile that they would collapse immediately. Scientists try to narrow their predictions down to just those that seem viable. “It filters down to fewer of them,” said Pickard, who worked on the simulation. “But the reality is, we don’t exactly know how to place that filter.”
To discover the forms that ice actually takes, scientists head to the laboratory.
Under Pressure
In 2018, Yong-Jae Kim was a postdoc at the Korea Research Institute of Standards and Science (KRISS) studying how room-temperature water turns to ice under extreme pressure. The experiment involved squeezing a drop of water between two diamonds and studying its changing molecular structure with high-speed imaging and other analysis techniques.
Going through the data from the experiment, Kim noticed what at first looked like a mistake. For just a few tens of milliseconds, the ice seemed to lose its structure, dissolving into a mess of molecules before transitioning to its next phase. Kim worried that sweat or dirt had contaminated the water. “At that stage, I felt more anxious than excited,” he said. He shared the observation with the rest of his team, but he ran out of time to follow up on it.
In 2025, researchers at KRISS ran an improved version of the same experiment using Kim’s diamond system and managed to re-create the strange structure. It was so complex that at first it looked almost random. “But step out,” Kim said, “and we see the structure macroscopically. It has a periodicity.”
The researchers took their setup to the European X-Ray Free-Electron Laser Facility in Germany, which houses a laser that accelerates electrons through a 3.4-kilometer-long tunnel and then sends them through special magnets to produce bursts of X-rays. “The brighter the beams of X-rays, the better pictures you get of your crystal structures,” Pickard said.
The scientists shone high-powered X-ray laser beams through the ice and measured how the beams scattered. Most phases of ice send the rays bouncing in just a couple different directions, since their crystal patterns repeat after a few molecules. But this sample sent the light along roughly 15 different paths. When the scientists analyzed the images, the number of molecules in the crystal pattern came to a whopping 152. The team’s observation of the structure earned the phase of ice an official Roman numeral name, ice XXI.
What’s more, the new phase was a total surprise. The team scoured the tens of thousands of phases predicted by Pickard’s group in search of a match, but they didn’t find one. The repeating structure of ice XXI, it turned out, was beyond the size at which the simulation capped its search. “They basically found something much more complicated than we did,” Pickard said.
Unbeknownst to the KRISS team, a group from Okayama University had actually predicted the structure in a different, narrower simulation also created in 2018. The more focused simulation predicted two additional phases of ice that are still undiscovered.
Changes
The researchers at KRISS and Kim, now at LLNL, had not set out to discover a new phase of ice. Rather, they wanted to investigate another of water’s strange properties, related to how it transitions from phase to phase. The classical theory of phase transitions predicts that any system will return to its lowest-energy state. But water does not always follow predictions.
For example, Kim’s sample did not respond to being squeezed by the diamond device by jumping straight to its most stable state, which at that level of pressure would be a form called ice VI. Instead, it hopped from water to ice XXI, and then to ice VII. These in-between phases are called metastable states, and their existence demonstrates that some phase transitions happen in steps, rather than all at once.
Water’s metastable states support a theory of phase transitions called Ostwald’s step rule, named for Wilhelm Ostwald, a German physical chemist and a peer of Albert Einstein. (Einstein was initially rejected for a job in Ostwald’s laboratory, but the two later became friends, and Ostwald eventually nominated Einstein for the Nobel Prize.) Ostwald’s step rule suggests that systems transition to the closest and easiest-to-reach phase state rather than the most thermodynamically stable one — and that they sometimes then get stuck. “It’s a nicely paradoxical thing that sometimes the easiest [state] to form is the one that’s the least stable,” Pickard said.
A group led by Hiroki Kobayashi of the University of Tokyo has already followed up on the discovery of ice XXI, as reported in a preprint article, by re-creating it using different techniques. In the process, they discovered a nearby phase — now dubbed ice XXII — that is even more complex, repeating its pattern only every 304 molecules.
At lower temperatures, the group also came up with a way to reliably produce ice IV, a metastable phase of ice so elusive that it has earned the name “will-o’-the-wisp,” after the ghostly lights that lure travelers in folk tales.
As scientists observe more metastable states, they are collecting evidence that this application of Ostwald’s theory accurately describes how phase transitions work, not just in ice but in other kinds of crystals, including those used in medicine. Changing the phase of a pharmaceutical drug can change its effectiveness, something factories need to protect against. “Sometimes drugs can turn from one [phase] to another and then ruin the whole batch,” Pickard said. Ostwald’s theory helps predict when that might happen.
Let’s Dance
In 2025, Bove’s team in Lausanne discovered a smaller but in some ways stranger metastable phase of ice. In a study published in Nature, they reported the first observation of plastic ice VII. This is a variation of ice VII, a high-pressure phase of ice, that appears when the ice is heated to around 500 degrees Celsius.
In plastic ice, water molecules retain their solid crystal structure but spin rapidly in place. This motion is difficult to observe; hydrogen is practically invisible to X-rays, which in water molecules deflect only off the atoms of oxygen. “If you can’t see the hydrogens, then you can’t really tell if the water molecule is rotating,” Pickard said.
So in addition to using X-rays, Bove’s team adopted a different technique: They sent a stream of neutrons into the hot ice. “Those neutron techniques are so powerful,” Millot said. “You can look at the molecules and see if they vibrate, if they rotate, if they vibrate and rotate.”
The rotating molecules in plastic ice VII give the ice some elasticity, like a gentle trampoline. Plastic ice VII is believed to exist inside the cores of icy moons and is thought to be an intermediate state that ice passes through before becoming a hotter form called superionic ice (or ice XVIII), first discovered in 2019. In this form, hydrogens fully break free of their bonds to oxygens, allowing the ice to conduct electricity.
Research like Bove’s shows that observing more of water’s phases might require using new experimental techniques or combining several different ones. Scientists are currently working on new methods to up the pressure they can apply to water. “The final pressure that we are aiming for is really high,” Coppari said, “more than twice the pressure at the center of the Earth.”
We live on the planet of water, but we’re still learning what water can do. “The more we look and the better the experiment becomes, the more surprises we find,” Millot said.