Diamond Formation in Giant Ice Planets

行星的内部结构，即物质的分布和密度，在很大程度上是由流体静力平衡决定的：在气体和冰雪巨星中，分别是木星和海王星，压缩的内部层的气体或等离子体压力必须保持上层的重量。因此，作为压缩函数的材料的相和压力是行星建模的主要成分。虽然上层由通常的气体组成，压缩程度越来越高，但行星的壁炉架大部分是电离的，这主要是由于材料的高度压缩。因此，我们既需要对高度压缩的中性气体，也需要对高压和中等温度(几千度)下的电离物质有很好的了解。气态和冰态巨星结构的最大变化与高压下的相变有关。这样的转变可以阻止对流(就像地球大气中的云的形成一样)，因此，可能会构成两侧成分不同的层边界。在冰巨星中，我们在可观察到的层中发现了丰富的气体成分：甲烷、氨或水。此外，实验和模拟已经发现，当这些材料被置于行星更深层的极端压力下时，会出现很大范围的相。最突出的预测之一是氢和碳从碳氢化合物中分离出来。基于这一预测，罗斯在1981年问道：天空中有钻石吗？30多年后，这个问题才能通过新的实验室实验得到肯定的回答。然而，行星内部的全部压力和温度范围太大，无法进行实验测试。在这方面，需要模拟和理论估计。该项目将基于最近关于结冰行星中碳(从石墨)和碳水化合物在高压下形成钻石的数据，并探索钻石形成和钻石雨对结冰行星的内部结构和能量平衡的可能后果，其中包括一些高碳含量的系外行星。需要回答的问题包括钻石的可能大小、它们出现的区域、钻石在引力场中下沉所释放的能量等。为了回答这些问题，需要建立一个新的演化模型。实验记录中的空白应该通过从头计算模拟(存在工具)来填补。此外，该项目还将通过预测和确定现有合作中的重要参数区域来支持新的试验活动。

The internal structure of a planet, that the distribution of material and its density, is largely defined by hydrostatic equilibrium: in gas and icy giants like Jupiter and Neptune, respectively, the gas or plasma pressure of the compressed internal layers must hold the weight of the upper layers. Therefore, the phase and the pressure of the material as a function of compression are the main ingredient for planet modelling. While the upper layers consist of usual gases that get more and more compressed, the mantel of the planet is ionised, mostly, due to the high compression of the materials. Accordingly, we need a good understanding of both highly compressed neutral gases as well as ionised matter under large pressures and at moderate temperature (few thousand degrees).The most dramatic change to the structure of gas and ice giants is related to phase transition at large pressures. Such transitions can prohibit convection (like the creation of clouds in the earths atmosphere) and, thus, may constitute layer boundaries with different compositions on each side. In ice giants, we find a rich composition of gases in the observable layers: methane, ammonia or water are present. Moreover, experiments and simulations have found a large range of phases when these materials are put under the extreme pressures of the deeper layers of the planets. One of the most prominent predictions was the phase separation of hydrogen and carbon from hydrocarbons. Based on this predictions, Ross ask in 1981 "Are there diamonds in the sky?". It took more than 30 years until this question could be answered positively by new laboratory experiments. However, the full range of pressures and temperatures inside a planet is too large to be tested experimentally. Here, simulations and theory estimates are needed.The project will be based on the recent data on diamond formation in carbon (from graphite) and carbohydrates the under large pressures in icy planets and explore possible consequences of diamond formation and diamond rain for the inner structure and energy balance of icy planets which includes a number of exoplanets with high carbon content. Question to be answered are the possible size of the diamonds, the region of their occurrence, the energy release due to the sinking diamonds in the gravitational field etc. To answer these questions, a new evolutionary model needs to be developed. Gaps in the experimental records should be closed by ab initio simulations (tools exist). Moreover, the project will also support new experimental campaigns by providing predictions and determination of important parameter regions within the existing collaboration.