Elements: NSCI-Software -- A General and Effective B-Spline R-Matrix Package for Charged-Particle and Photon Collisions with Atoms, Ions, and Molecules

该项目涉及一套计算机代码的开发和随后的分发，这些代码可以准确地描述带电粒子（主要是电子）和光（主要是激光和同步加速器）与原子和离子的相互作用。这些结果对于理解基本碰撞动力学具有重要意义，它们也满足了对精确原子数据的迫切实际需求，以模拟恒星，等离子体，激光和行星大气的物理。随着计算资源的快速发展，这种研究现在可以针对现实系统进行，而不是理想化的模型。特别是，它已经成为可能，以描述非常复杂的目标，如过渡金属和其他开壳系统。例子包括氦以外的惰性气体的激发态，以及中性和低电离铁。 这些系统分别对等离子体诊断和天体物理学具有重要意义。 源代码将公开提供。该项目将资助一名博士后研究员。将开发和维持一个专门用于用户-开发人员互动的网站，同时提供必要的代码文件和培训材料，数值计算将以非微扰R矩阵（紧密耦合）方法为基础。 在这个项目中所追求的实施的一个特别的优势是使用一个高度灵活的B样条的基础上，非正交轨道集。 与传统方法相比，该方法的主要优点是，如果放松对各个轨道的正交性要求，则可以通过大大减少的构型相互作用（CI）展开来实现准确的目标描述。 这对于复杂的目标是至关重要的，其中特别是已知的价轨道是强烈的术语依赖性。使用足够小但仍然足够精确的目标状态CI扩展对于后续碰撞计算的可行性和质量至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估而被认为值得支持。

This project concerns the development and subsequent distribution of a suite of computer codes that can accurately describe the interaction of charged particles (mostly electrons) and light (mostly lasers and synchrotrons) with atoms and ions. The results are of importance for the understanding of fundamental collision dynamics, and they also fulfill the urgent practical need for accurate atomic data to model the physics of stars, plasmas, lasers, and planetary atmospheres. With the rapid advances currently seen in computational resources, such studies can now be conducted for realistic systems, as opposed to idealized models. In particular, it has become possible to describe very complex targets, such as transition metals and other open-shell systems. Examples include the excited states of the inert gases beyond helium, as well as neutral and lowly-ionized iron. These systems are of significant importance for plasma diagnostics and astrophysics, respectively. The source code will be made publicly available. The project will support a post-doctoral researcher. A website devoted to user-developer interaction will be developed and maintained together with the neccessary code documentation and training materials.The numerical calculations will be based upon the non-perturbative R-matrix (close-coupling) method. A particular strength of the implementation pursued in this project is the use of a highly flexible B-spline basis with non-orthogonal orbital sets. The major advantage of the approach compared to traditional methods is the fact that an accurate target description can be achieved with a much-reduced configuration-interaction (CI) expansion if the orthogonality requirements on the individual orbitals are relaxed. This is critical for complex targets, where the valence orbitals in particular are known to be strongly term-dependent. Using a sufficiently small but still accurate enough CI expansion for the target states is essential for the feasibility and quality of the subsequent collision calculation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.