Prediction and characterization of novel Earth-forming minerals using advanced ab initio simulations

人类在研究外层空间和原子物质的内部运作方面取得了很大进展，但我们赖以生存的星球仍然是一个谜。地球的深处隐藏着我们，无法直接探测，它定义了我们星球的面貌，并深刻地影响了我们的日常生活(通过地震、火山活动和使生命免于太阳风的磁场)。只有通过地震学、地球化学学和矿物物理学的结合，才能在地球深部研究方面取得进展。计算矿物物理学最近取得了很大进展，量子力学方法的发展使人们能够研究与地球有关的复杂化学，并对在行星内部典型的高压和温度下发生的新的化学现象做出公正的预测。该项目旨在借助先进的量子力学方法更好地了解地球的化学和物理。这种方法非常普遍，最近在计算设计新材料方面取得了突破，这对我们的社会具有潜在的变革价值。这项研究连接了地球科学、材料科学、物理和化学等多个领域，并专注于激发人类好奇心的问题(地球是由什么组成的，地球是如何形成的)。如果没有年轻科学家的精力，这些研究是不可能的，他们将在这个多学科的科学领域得到独特的培训，并将在这些领域中的任何一个领域完美地为世界服务。对地球深层的研究是现代研究中最吸引人的领域之一。目前，经过几十年的不断努力，地球深部的矿物学模型终于建立起来了。来自地震层析成像和矿物物理的数据可以很好地估计地球深处的热变化和成分变化。矿物物理学提供了有关地球形成矿物的物理性质以及它们对温度和成分的依赖的信息，以及矿物体系的相图。地球形成矿产的勘探是地球科学中最关键的问题之一。尽管在实验高压技术方面取得了巨大的进步，但大多数对地球深部地幔和地核压力的物理测量都是有问题的。最近，一直被认为稳定存在于地球深部地幔中的(Mg，Fe)SiO_3钙钛矿被发现分解成镁硅钙钛矿和富铁六方相(H相，其晶体结构仍有争议)。PI的初步结果表明，令人惊讶的结果是，在Mg-Si-O系统中，钛铁矿和钙钛矿的MgSiO_3在30 GPa0Kelvin时都是热力学不稳定的，而在30 Gpa时根本不存在其他三元稳定化合物，这表明可以观察到一个非常重要的意外现象，并可能对神秘的地震特征产生重大影响。此外，除了众所周知的410,520,660公里处的地震不连续外，在差异很大的地区也可以看到另一个800公里的地震不连续，但到目前为止还没有合理的解释，可能会出现另一个未知的阶段。地幔中的矿物可能比我们目前所知的更复杂。基于量子力学的理论模拟在地球科学中发挥着越来越重要的作用。因此，PI将应用计算物理中最先进和最新发展的工具来解决与地幔、核和核幔边界区域有关的问题。PI将集中于三个问题：(1)在三元系甚至更高的多组分系统中向变化学计量比材料预测的方法学发展。PI最近的工作表明，基于进化方法的二进制系统预测是容易处理的。由于地球科学中的一些重要矿物具有令人费解的化学计量学，剩下的挑战是在高P-T条件下预测稳定的三元、四元甚至更高的多组分体系。(2)在给定的P-T条件下，预测了Mg-Fe-Ca-Al-Si-O和Fe-Si-C-S-H-O系统的成地矿物。由于真实地幔中的钙钛矿相和后钙钛矿相成分复杂，Ca、Al和C等附加元素也会影响相的结构和稳定场。因此，将讨论多组分体系的晶体结构预测。将计算地幔和地核中形成地球的矿物的性质。无法解释的地震不连续和H相的性质有望被发现，在地幔和核中很可能发现一些新的矿物。(3)地幔与核之间的化学反应。这项研究将大大加深我们对铁基合金的了解，将使我们更好地了解地核的化学和矿物学，以及它的特殊性质(如强烈的地震各向异性)。了解核-地幔边界区域可能发生的反应可能有助于了解该区域的某些反常性质。简而言之，这个项目将使用先进的量子力学模拟来研究地球上最神秘的地区的材料。这项研究的核心是PI的进化算法USPEX，它与第一原理电子结构计算相结合。这种方法已经在矿物学和物理学中产生了许多重要的预测，并被随后的实验成功地证实。

Humans have greatly advanced in the study of the outer space and inner workings of atomic matter, but the very planet upon which we live remains a mystery. Hidden from us and impossible to probe directly, Earth's deep interior has defined the face our planet and profoundly influences our daily life (through earthquakes, volcanism, and the magnetic field that saves life from solar wind). Progress in studies of the Earth's deep interior can only be made through a combination of seismology, geochemistry, and mineral physics. Computational mineral physics has made great progress recently, with the development of quantum-mechanical methods allowing one to study complex chemistry pertinent to the Earth, and make unbiased predictions of novel chemical phenomena that take place under high pressures and temperatures typical of planetary interiors. This project aims toward a better understanding Earth's chemistry and physics with the help of advanced quantum-mechanical methods. Such methods are quite universal and recently have led to breakthroughs in the computational design of novel materials, which have a potentially transformative value for our society. This research bridges several the fields of geosciences, materials science, physics, and chemistry, and focuses on problems that excite curiosity of humans ("what is the Earth made of", "how was the Earth formed"). Such studies are impossible without the energy of young scientists who will get unique training in this multidisciplinary field of science and will be perfectly equipped to serve the world in any of these fields. The study of the Earth's deep interior is one of the most fascinating fields of modern research. Currently, based on several decades continuing works by geoscientists, reasonable mineralogical models of the deep Earth are finally constructed. Thermal and compositional variations in the deep Earth can be well estimated by data from seismic tomography and mineral physics. Mineral physics provides information about the physical properties of Earth-forming minerals together with their dependence on temperature and composition, and phase diagrams of mineral systems. Exploration of the Earth-forming minerals is one of the most critical issues in Earth sciences. Despite tremendous progress in experimental high-pressure techniques, most physical measurements at pressures of the Earth's deep mantle and core are problematic. Recently, (Mg,Fe)SiO3 perovskite, long believed to be stable in the Earth's deep lower mantle, was found to decompose into MgSiO3 perovksite and an Fe-rich hexagonal phase (H-phase, the crystal structure of which is still debatable). The PI's preliminary results show the surprising result that both ilmenite MgSiO3 and perovskite MgSiO3 are thermodynamically unstable at 30 GPa 0 Kelvin in the Mg-Si-O system, and no other ternary stable compounds exist at 30 GPa at all, which indicates a very important unexpected phenomenon can be observed and significant implications for enigmatic seismic features might be expected. Furthermore, besides the well-known seismic discontinuities at 410, 520, 660 km, another seismic discontinuity at 800 km is also seen in widely varying regions, but so far has no reasonable explanation, and another unknown phase might be expected. Minerals in the mantle are probably more complex than what we know currently. Theoretical simulations based on quantum mechanics have played an increasingly important role in Earth sciences. Therefore, the PI will apply the most advanced and recently developed tools in computational physics to address problems related to the mantle, core and core-mantle boundary region.The PI will focus on three problems: (1) Methodology development toward the prediction of materials with variable stoichiometry in ternary and even higher multi-component systems. The PI's recent work has shown that the prediction of binary systems based on the evolutionary approach is tractable. Since a number of important minerals in the context of earth sciences have puzzling stoichiometry, the remaining challenge is to predict stable ternary, quaternary and even higher multi-component systems at high P-T conditions. (2) Prediction of Earth-forming minerals in the Mg-Fe-Ca-Al-Si-O and Fe-Si-C-S-H-O systems under given P-T conditions. Since the perovskite and post-perovskite phases in the real mantle have complex compositions, additional elements, like Ca, Al and C, can also affect the structure and stability field of phases. Therefore, crystal structure predictions for multicomponent systems will be addressed. Properties of Earth-forming minerals in the mantle and core will be computed. The nature of unexplained seismic discontinuities and H-phase are expected to be uncovered and some novel minerals are highly likely to be discovered in the mantle and core.(3) Chemical reactions between the mantle and core. This study should greatly deepen our understanding of iron-based alloys, will lead to better understanding of chemistry and mineralogy of the Earth's core, as well as its peculiar properties (such as strong seismic anisotropy). Understanding of possible reactions at the core-mantle boundary region may shed light on some of the anomalous properties of that region. In short, this project will look at materials of the most enigmatic regions of the Earth using advanced quantum-mechanical simulations. Central to this study is the PI's evolutionary algorithm USPEX, interfaced with first-principles electronic structure calculations. This approach has produced many important predictions in mineralogy and physics, successfully confirmed by subsequent experiments.