Towards a Merger of Nonadiabatic Molecular Dynamics and Spintronics

宾夕法尼亚大学的Joseph Subotnik得到了化学系化学理论，模型和计算方法项目的支持，研究电子自旋如何影响核弛豫，并通过产热形成能量损失。 特别是，Subotnik将开发新的和强大的算法，精确量化具有原子核和自旋的分子在被光激发后如何放松。 Subotnik将在理论上和计算上测试哪些原子在弛豫期间移动，并将探索这种原子运动可能导致长时间促进自旋选择性的可能性。 所有的算法开发都将以开源的方式向公众发布。 该研究项目处于物理化学和自旋化学的前沿，从长远来看，这里的研究有可能帮助创建一种全新形式的基于电子自旋的电子器件（所谓的自旋电子学），而不是基于电子电荷的传统器件。更广泛的影响包括Subotnik小组支持将本科研究人员带入实验室，特别强调将代表性不足的群体成员引入实践科学。 Subotnik研究团队还邀请这些学生参加一年一度的宾夕法尼亚大学理论化学会议（PCTC）。Subotnik将开发一种半经典算法，用于量化在存在自旋轨道耦合的情况下，脱离平衡的耦合核电子系统如何放松。在存在自旋轨道耦合的情况下，电子哈密顿量变得复值，并且电子跃迁的性质对于现代算法变得非常困难，因为（i）动量重新标度的方向变得不清楚，以及（ii）Berry磁力的存在可能导致新的反应途径。 Subotnik正在构建和基准测试一种新的，可靠的表面跳跃方法来处理这种情况，既适用于双重态（具有两个电子态）的情况，也适用于单重态-三重态交叉（具有四个电子态）的情况。 此外，Subotnik还将在相当小的测试案例上进行模拟，以研究核电子动力学耦合效应（包括Berry力）的存在是否可能成为最近显示手性诱导自旋选择性（CISS）效应的实验的基础。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Joseph Subotnik of The University of Pennsylvania is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to study how electronic spin affects nuclear relaxation and can shape energy loss via heat production. In particular, Subotnik will develop new and powerful algorithms that quantify exactly how molecules with nuclei and spins relax after they have been excited by light. Subotnik will test both theoretically and computationally which atoms move during relaxation, and will explore the possibility that this atomic motion can lead to a promotion of spin-selectivity for long periods of time. All of the algorithmic developments will be released to the public in an open source fashion. This research program lies at the cutting edge of physical chemistry and spin-chemistry, and in the long term, research here has the potential to help create an entirely new form of device electronics based on electronic spin (so-called spintronics) unlike conventional devices based on electronic charge. The broader impacts include the Subotnik group's support for bringing undergraduate researchers into the lab, with a special emphasis on introducing members of underrepresented groups to hands-on science. The Subotnik research team also invites these students to participate the annual Penn Conference in Theoretical Chemistry (PCTC). Subotnik will develop a semi-classical algorithm for quantifying how coupled nuclear-electronic systems prepared out of equilibrium relax in the presence of spin-orbit coupling. In the presence of spin-orbit coupling, the electronic Hamiltonian becomes complex-valued and the nature of electronic transitions becomes very difficult for modern algorithms because (i) the direction of momentum rescaling becomes unclear and (ii) the presence of Berry magnetic forces can lead to novel reaction pathways. Subotnik is constructing and benchmarking a novel, reliable surface hopping approach to treat such conditions, both for the case of doublets (with two electronic states) as well as for the case of singlet-triplet crossings (with four electronic states). Furthermore, Subotnik will run simulations on reasonably small test cases to investigate whether the presence coupled nuclear-electronic dynamics effects (including Berry forces) may underlie recent experiments displaying a chiral induced spin selectivity (CISS) effect.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.