Molecules in Non-Perturbative Fields: Improving Time-Dependent Density Functional Approximations and Electron-Ion Correlation Methods

CUNY Hunter学院的Neepa Maitra得到了化学系化学理论、模型和计算方法计划的支持，该计划旨在开发理论和计算方法来模拟电子和离子的关联动力学。材料研究部的凝聚态物质和材料项目也为这一奖项做出了贡献。了解电子和离子的运动对于理解和预测许多涉及物质与光的相互作用的现象很重要。这些现象既有基础也有技术上的重要性，例如，将光转化为电能的光伏器件、光催化和使用激光控制化学过程。支配这一运动的方程式已经知道了90年。然而，对于除了最简单的系统之外的所有系统，精确地求解这个方程都太难了。这一困难是由于相关运动引起的。每个电子的运动都会影响其他电子的运动，也会影响每个离子的运动，反之亦然。含时密度泛函理论(TDDFT)是求解该方程的一种有效、近似和流行的方法。在许多情况下，今天使用的特殊近似是不充分的，导致电子动力学中不可预测的误差。Maitra和她的同事基于严格的理论考虑开发了改进的近似。本科生和研究生都参与了这项前沿研究。Maitra在CUNY组织了小型研讨会，向更广泛的纽约地区的科学家开放。她与亨特学院现有的项目合作，促进代表不足的少数族裔科学家的发展Maitra和她的同事通过施加精确条件来开发改进的、健壮的电子动力学近似，以便该理论可以用于实时动力学，其置信度和可预测性与密度泛函理论用于基态能量和结构一样多。我们的目标是克服TDDFT的几个限制，这些限制目前阻止它可靠地用于非微扰区域的实时电子动力学以及激发光谱。电子和离子的动力学耦合是基于最近引入的第一原理精确因式分解方法。这包括为关联电子-离子动力学开发实用的混合量子(半)经典方案，其中包括电子退相干和从第一原理开始的波包分支。

Neepa Maitra of CUNY Hunter College is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop theoretical and computational approaches for simulating the correlated dynamics of electrons and ions. The Condensed Matter and Materials program in the Division of Materials Research also contributes to this award. Understanding the motion of electrons and ions is important for understanding and predicting many phenomena that involve the interaction of matter with light. These phenomena have both fundamental and technical importance, for example, photovoltaic devices which convert light into electricity, photocatalysis, and control of chemical processes using lasers. The equation that governs this motion has been known for 90 years. For all but the simplest systems, however, it is too difficult to solve this equation exactly. This difficulty arises because of correlated motion. Each electron's motion affects every other electron's motion as well as each ion's, and vice-versa. Time-dependent density functional theory (TDDFT) is an efficient, approximate and popular approach to solving this equation. In many cases, the particular approximations used today are not adequate, causing unpredictable errors in the electron dynamics. Maitra and her coworkers develop improved approximations based on rigorous theoretical considerations. Both undergraduate and graduate students participate in this cutting-edge research. Maitra organizes mini-workshops at CUNY open to scientists in the wider New York area. She works with existing programs at Hunter College to promote the development of underrepresented minority scientists Maitra and her coworkers develop improved, robust approximations for electron dynamics by imposing exact conditions, so that the theory can be used for real-time dynamics with as much confidence and predictability as density functional theory is used for ground-state energies and structures. The goals is to overcome several limitations of TDDFT that currently prevent it from being used reliably for real-time electron dynamics in the non-perturbative regime, as well as for excitation spectra. The dynamics of the electrons and ions are coupled by using a method based on the recently-introduced first-principles exact factorization approach. This includes developing practical mixed quantum-(semi)classical schemes for correlated electron-ion dynamics that include electronic decoherence and wave packet-branching from first-principles.