Diamond Formation in Giant Ice Planets

行星的内部结构，即物质的分布及其密度，在很大程度上是由流体静力学平衡定义的：在木星和海王星这样的气体和冰巨星中，压缩内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位和压力是行星建模的主要成分。虽然上层由越来越压缩的普通气体组成，但由于材料的高度压缩，行星的地幔被电离。因此，我们需要很好地理解高压和中等温度（几千度）下的高度压缩中性气体和电离物质。气体和冰巨星结构最显著的变化与高压下的相变有关。这种转变可以阻止对流（就像地球大气中云的形成一样），因此，可能会构成每一侧成分不同的层边界。在冰巨星中，我们在可观察的层中发现了丰富的气体成分：甲烷，氨或水。此外，实验和模拟发现，当这些材料处于行星深层的极端压力下时，会出现大范围的相态。最突出的预测之一是碳氢化合物中氢和碳的相分离。1981年，罗斯问：“天上有钻石吗？”".这个问题花了30多年的时间才得到新的实验室实验的肯定回答。然而，行星内部的压力和温度范围太大，无法通过实验进行测试。该项目将基于最近关于在冰冷行星的巨大压力下碳（来自石墨）和碳水化合物中形成金刚石的数据，并探索金刚石形成和金刚石雨对冰冷行星内部结构和能量平衡的可能影响，其中包括一些具有高碳含量的系外行星。需要回答的问题是钻石的可能大小，它们的出现区域，由于下沉的钻石在引力场中的能量释放等，要回答这些问题，需要开发一个新的进化模型。实验记录中的空白应通过从头算模拟来填补（已有工具）。此外，该项目还将通过在现有合作范围内提供重要参数区域的预测和确定来支持新的实验活动。

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.