基于无轨道密度泛函理论的OEPP赝势与实空间ATLAS计算软件

发布时间：2019-04-26 21:47

【摘要】：无轨道密度泛函理论(Orbital-free density functional theory,OF-DFT)是以量子力学为基础,仅根据电子密度就可以精确求解多电子体系基态性质的理论。同传统基于轨道的Kohn-Sham密度泛函理论(KS-DFT)相比,由于不需要轨道(波函数)信息,其计算量随模拟体系的大小呈线性变化。因此OF-DFT可以突破传统KS-DFT模拟尺度的极限(约千原子量级),成为适合于开展包含百万以上原子的大尺度材料模拟的第一性原理计算方法。目前,KS-DFT框架下发展成熟的非定域赝势由于包含轨道信息,无法在OF-DFT中直接应用。因此,构建不包含轨道信息的定域赝势是应用OF-DFT开展研究需解决的一个关键问题。另外,与KS-DFT的发展相比较OF-DFT相对滞后,相应的计算软件非常稀缺,严重阻碍OF-DFT在材料模拟中的广泛应用,因此完善OF-DFT理论,发展相应的材料模拟软件是应用OF-DFT开展研究需解决的另一个关键问题。本论文作者与课题组其他成员合作针对以上两个关键问题进行了系统研究,获得了如下创新性成果:1.利用优化有效势方法结合保模条件,从理论上揭示出(非定域)保模赝势与定域赝势之间的本质关系,并基于此基本关系,发展了一种从保模赝势出发,只需利用单原子电子结构信息,就可以构建第一性原理的优化有效定域赝势(OEPP)方法。研究发现,在元素周期表中(除第二周期元素外)的大多数s和p型元素都可以利用我们的方法构建出具有高移植性定域赝势。另外,我们的研究还发现,某种元素能否构建出高移植性的定域赝势是该元素的固有属性,与构造方法无关。2.利用实空间有限差分方法结合能量直接最小化算法,发展出基于OF-DFT的适合于大尺度材料计算的第一性原理方法,并在此基础上,开发了拥有自主知识产权的计算软件ATLAS,受中国版权局的计算机软件著作权保护(登记号:2016SR027209)。由于采用实空间差分方法,该软件的并行效率和处理各种边界条件的能力可以显著提高,而能量直接最小化算法的引入可以保证对大尺度材料模拟的数值稳定性。目前ATLAS软件的计算效率、精度和稳定性已经通过Mg、Al和Mg-Al合金体系进行了测试和验证。
[Abstract]:Orbital density functional theory (Orbital-free density functional theory,OF-DFT) is based on quantum mechanics and can be used to accurately solve the ground state properties of multi-electron systems based on the electron density alone. Compared with the conventional orbital-based Kohn-Sham density functional theory (KS-DFT), the computational complexity varies linearly with the size of the simulation system because the orbital (wave function) information is not required. Therefore, OF-DFT can break through the limit of traditional KS-DFT simulation scale (about thousands of atoms) and become the first-principle calculation method suitable for the simulation of large-scale materials containing more than one million atoms. At present, the mature non-local pseudopotential under the framework of KS-DFT can not be directly applied in OF-DFT because it contains orbital information. Therefore, the construction of local pseudopotential without orbital information is a key problem to be solved in the application of OF-DFT. In addition, compared with the development of KS-DFT, OF-DFT lags behind, and the corresponding computing software is very scarce, which seriously hinders the extensive application of OF-DFT in material simulation. Therefore, the theory of OF-DFT is perfected. The development of the corresponding material simulation software is another key problem to be solved in the research with OF-DFT. In collaboration with other members of the research group, the author of this paper has carried out a systematic study on the above two key issues, and has obtained the following innovative results: 1. Based on the optimized effective potential method and the mode-preserving condition, the essential relationship between the (non-local) module-preserving pseudopotential and the local pseudopotential is revealed theoretically. Based on this basic relation, a new model-preserving pseudopotential is developed, which is based on the model-preserving pseudopotential. The first-principle optimization and effective local pseudopotential (OEPP) method can be constructed only by using the information of the electronic structure of a single atom. It is found that most of the s and p-type elements in the periodic table (except for the second periodic elements) can be used to construct a highly portable local pseudopotential. In addition, we also found that whether an element can construct a highly transplantable local pseudopotential is an inherent attribute of the element and has nothing to do with the construction method. By using the finite difference method in real space and the direct energy minimization algorithm, a first principle method suitable for large scale material calculation based on OF-DFT is developed. On the basis of this, a computing software ATLAS, with independent intellectual property rights is developed. Copyright protection of computer software by China copyright Administration (registration number: 2016SR027209). The parallel efficiency of the software and the ability to deal with various boundary conditions can be greatly improved by using the real-space difference method, and the introduction of the direct energy minimization algorithm can ensure the numerical stability of the large-scale material simulation. At present, the calculation efficiency, accuracy and stability of ATLAS software have been tested and verified by Mg,Al and Mg-Al alloy systems.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O413.1

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