Development of Next-Generation Relativistic Program for All-Order Treatment of Many-Electron Systems

原子和分子结构与碰撞的定量理解是理论原子和分子物理学研究的主要领域之一。这一领域的研究成果为广泛的基础和应用科学领域（包括天体物理学、等离子体科学和量子信息）的基础理论和实验研究提供了关键输入。此外，这项研究与具有重要社会意义的重要实际应用相关，例如为GPS系统开发更好的时钟。迄今为止，这一领域的成功主要局限于对较简单的原子系统的研究；对于元素周期表中更复杂的原子，还没有达到类似的认识水平。该项目侧重于开发一种高精度的理论和计算方法，旨在将对过渡金属复杂原子的理论理解提高到目前只提供给更简单的原子系统的相同复杂水平。如果成功的话，这一结果将为元素周期表的大部分元素打开应用的大门，而迄今为止，这些元素只能用最简单的原子来研究。因此，该项目为学生和博士后在物理学前沿科研课题的培训提供了充足的机会。本项目旨在基于大尺度构型相互作用和全阶线性化耦合簇方法的结合，开发下一代完全相对论性的广泛适用的原子代码，能够以百分之几的精度预测开壳原子的性质。该代码的主要特点是能够处理目前无法准确描述原子性质的系统。虽然近年来在高精度原子计算方面取得了巨大的进展，但处理d壳层和f壳层开放系统的相关性对AMO理论提出了前沿挑战。本项目将解决当前处理d壳层和f壳层原子开放系统中相关关系的方法的以下缺点：遗漏三体相互作用，有限的起始势选择，以及需要有效地选择最重要的构型来构建非常大的构型空间。由此产生的代码将能够计算广泛的原子性质，包括能量、g因子、超精细常数、各种跃迁矩阵元素、电偶极子和电四极子静态和动态极化率、远程相互作用势参数、各种P（宇称）奇和T（时间）奇效应、精细结构常数变化测试的灵敏度因子和局部洛伦兹不变性的原子测试。新一代代码的性能将在具有多个价电子的系统中进行测试。

The quantitative understanding of atomic and molecular structure and collisions represents one of the main areas of research in theoretical atomic and molecular physics. Results from this area of research form key input to fundamental theoretical and experimental studies in a broad range of basic and applied scientific fields, including astrophysics, plasma science, and quantum information. In addition, this research is relevant for important practical applications with important societal implications, such as the development of better clocks for GPS systems. To date success in this area has been primarily restricted to studies of the simpler atomic systems; comparable levels of understanding have not been achieved for more complex atoms in the Periodic Table. This project focuses on developing a high-precision theoretical and computational approach that seeks to bring the theoretical understanding of complicated atoms of transition metals to the same level of sophistication afforded presently only to much simpler atomic systems. If successful, the results could open up much of the Periodic Table to applications that heretofore could only be pursued with the simplest atoms. As such, this project provides ample opportunities for the training of students and post-doctoral fellows on topics at the leading edge of scientific research in physics. This project aims to develop a next-generation fully relativistic broadly applicable atomic code, based on the combination of large-scale configuration interaction and all-order linearized coupled-cluster method capable of predicting properties of open-shell atoms with precision of a few percent. The main feature of the code is to be able to treat systems where no accurate description of atomic properties is presently possible. While tremendous progress has been made recently in high-precision atomic calculations, treatment of correlation in d- and f-shell open systems present frontier challenges to AMO theory. This project will address the following short comings of current approaches needed for the treatment of correlations in d- and f-shell atomic open systems: omission of three-body interactions, limited choice of the starting potential, and the need for efficient selection of most important configurations for the construction of very large configuration spaces. The resulting code will be able to calculate a wide range of atomic properties including energies, g-factors, hyperfine constants, various transition matrix elements, electric-dipole and electric-quadrupole static and dynamic polarizabilities, long-range interaction potential parameters, various P(parity)-odd and T(time)-odd effects, sensitivity factors for tests of variation of the fine-structure constant and atomic tests of local Lorentz invariance. The performance of the new-generation code will be tested for systems with several valence electrons.