Investigating the Density of a Chondritic Melt Under High Pressure, and Implications for Earth Formation

确定地球最初的岩浆海洋是如何结晶成固体的，对于了解地球演变到今天的状态很重要。控制岩浆海洋结晶的基本性质之一是结晶矿物和熔融相之间的相对密度。这是因为相对密度控制着熔体是漂浮还是下沉，以及例如，是否形成孤立的基底岩浆海洋。然而，随着结晶的发生，熔体相的组成不断变化，特别是对于与初始熔体有很大不同的最终熔体。因此，在比固相更宽的组成范围内需要熔体的密度。预测任何组成的密度的困难之一是，像Birch-Murnagham这样的正常状态方程很难推广到任意组成。此外，由于在处理液体样品时的实验困难，这些熔体成分的实验数据有限。因此，我的项目将从从头计算中获得热力学数据，然后使用机器学习对这些数据进行拟合，以产生一个模型，可以描述岩浆海洋空间内任何给定压力、温度和成分的密度。

Determining how the Earth's initial magma ocean crystalised into a solid body is important for understanding Earth's evolution to its present-day state. One of the fundamental properties governing the crystalisation of the magma ocean is the relative density between the crystalizing minerals and the melt phase. This is because the relative densities control whether melts float or sink, and whether, for instance, an isolated basal magma ocean form. However, the composition of the melt phase continually changes as crystallization occurs, particularly for the final melts which are very different from the initial melt. As such the density of melts are needed over a much wider range of compositions than the solid phases. One of the difficulties with predicting densities at any compositions is that normal equations of state such as the Birch-Murnagham are difficult to extend to arbitrary composition. Furthermore, there is limited experimental data for these melt compositions, due to experimental difficulties when working with a liquid sample. As such, my project will obtain thermodynamic data from ab initio calculations, then using machine learning this data will be fitted, to produce a model that can describe the density, for any given pressure, temperature, and composition within the space of the magma ocean.