CALYPSO结构预测方法在高压材料和行星科学中的几个典型应用

发布时间：2018-10-26 20:36

【摘要】：凝聚态物质结构的理论预测是材料、物理和化学等学科长期关注的挑战性课题.论文作者和课题组其他成员合作，基于粒子群多目标优化算法,引入结构表征的成键特征矩阵,提出并发展了卡里普索(CALYPSO)结构预测方法,编制了具有自主知识产权的CALYPSO结构预测软件,现已成为国际结构预测领域的重要方法和工具.在此基础上,论文对材料和行星科学的典型体系进行了示范性的研究,获得了如下创新性结果: 1.三碲化二铋(Bi2Te3)在常压下是一种性能优良的热电材料，也是一种典型的拓扑绝缘体，其研究备受关注.自1972年以来,实验就发现Bi2Te3在高压下存在两个结构相变，并伴随着超导电性的出现.对超导电性产生根源的理解，必须弄清高压新相的结构.论文利用自主发展的CALYPSO结构预测方法预言Bi2Te3的两个高压相是分别具有7配位铋和8配位铋的单斜结构，并得到了高压X射线衍射实验的证实，研究工作解决了困扰近40年的Bi2Te3高压结构的难题.同时在14.4万大气压以上,论文发现Bi2Te3竟然转变为一个具有无序体心立方结构的Bi- Te替代合金. 2.作为物理、化学以及行星科学研究领域的长期主题，双原子分子固体的压致分子解离是人们长期关注的主题.论文利用CALYPSO结构预测方法,首次在1900万大气压下从理论上实现了固态氧的双原子分子解离，固态氧转变为螺旋链状的原子相结构.令人意外的是，固态氧的分子解离导致了固态氧从金属相到绝缘相的转变,违背了高压金属化的传统理念. 3.研究表明,在地球大气层中90%的氙气(Xe)不知去向,这就是行星学中著名的“Missing Xe Paradox”，即“氙气消失之谜”.人们普遍认为Xe存储在地球内部，但存在的位置和形态是地学领域长期争议的课题.1997年《科学》期刊发表了理论和实验合作论文，认为Xe和铁（地核的主要构成元素）无法反应形成稳定的化合物，排除了Xe存储在地核内部的可能性.论文利用CALYPSO结构预测方法，首次从理论上提出Xe可以与铁和镍在地核的压力和温度条件下发生化学反应，形成一系列稳定的化合物(例如, XeFe3, XeFe5, XeNi3, XeNi5等等).论文研究结果推翻了前期Xe和铁无法反应的论断,认为地核可以是氙气的藏身之所,很可能为“氙气消失之谜”提供了答案. 4.地球内部的地核是由85%的铁元素，，5%的镍元素和10%的轻质元素构成，氧也是地核中主要存在的轻质元素之一.长期以来,人们普遍认为在内地核中稳定存在的铁氧化合物为FeO.然而,在内地核的环境下,铁氧化合物究竟以什么形式存在仍然有待探索.我们利用CALYPSO结构预测方法研究了元素氧在内地核的富铁环境中可能的存在形式.研究发现在内地核中稳定存在的铁氧化合物并不是普遍认为的FeO,而应该是Fe3O.此研究工作为人们理解地球内核的结构提供了重要的理论依据.
[Abstract]:The theoretical prediction of condensed matter structure is a challenging subject in materials, physics and chemistry. Based on particle swarm optimization (PSO), the author and other members of the research group proposed and developed the Carripsos (CALYPSO) structure prediction method by introducing the bond-forming characteristic matrix of structural representation. The CALYPSO structure prediction software with independent intellectual property rights has been developed and has become an important method and tool in the field of international structure prediction. On this basis, the typical systems of materials and planetary science are studied in this paper, and the following innovative results are obtained: 1. Bismuth tritelluride (Bi2Te3) is a kind of excellent thermoelectric material and a typical topological insulator under atmospheric pressure. Since 1972, it has been found that there are two structural phase transitions in Bi2Te3 at high pressure, accompanied by the appearance of superconductivity. To understand the origin of superconductivity, it is necessary to understand the structure of the new phase at high voltage. In this paper, the independently developed CALYPSO structure prediction method is used to predict that the two high pressure phases of Bi2Te3 are monoclinic structures with 7 coordinated bismuth and 8 coordinated bismuth, respectively, and confirmed by high pressure X-ray diffraction experiments. The research work has solved the difficult problem of Bi2Te3 high pressure structure which has been puzzling for nearly 40 years. At more than 144000 atmospheres, it is found that Bi2Te3 is transformed into a Bi- Te substitute alloy with disordered body-centered cubic structure. 2. As a long-term topic in physics, chemistry and planetary science, the decompression molecular dissociation of diatomic molecular solids has long been the focus of attention. In this paper, the diatomic molecular dissociation of solid oxygen is theoretically realized at 19 million atmospheres by using CALYPSO structure prediction method, and the solid oxygen is transformed into a spiral chain atomic phase structure. Surprisingly, the molecular dissociation of solid oxygen leads to the transition of solid oxygen from metal to insulating phase, contrary to the traditional idea of high pressure metallization. 3. The study shows that 90% of the xenon (Xe) is missing in the Earth's atmosphere, which is known as "Missing Xe Paradox" in planetary science, or "the enigma of the disappearance of xenon". It is generally believed that Xe is stored in the interior of the earth, but the location and shape of the existence is a subject of long controversy in the field of geoscience. It is considered that Xe and iron (the main elements in the core) cannot react to form stable compounds, which excludes the possibility of Xe stored in the core. By using CALYPSO structure prediction method, it is proposed that Xe can react with iron and nickel at the pressure and temperature in the core for the first time to form a series of stable compounds (for example, XeFe3, XeFe5, XeNi3, XeNi5, etc.). The results of this paper refute the previous conclusion that Xe and iron cannot react, and that the core can be a hiding place for xenon, which may provide an answer to the mystery of the disappearance of xenon. 4. The core of the earth is composed of 85% of iron, 5% of nickel and 10% of light elements. Oxygen is also one of the main light elements in the core. For a long time, it has been widely believed that ferrite compounds that exist stably in inland nuclei are FeO. However, the form in which ferrite compounds exist in the inland nuclear environment remains to be explored. We have studied the possible forms of elemental oxygen in iron-rich environments in inland nuclei by using CALYPSO structure prediction method. The study found that ferrite compounds stably present in inland nuclei are not generally considered FeO, but should be Fe3O. This work provides an important theoretical basis for people to understand the structure of the earth's core.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：O521.2

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