Accurate Treatment of Strong Electron Correlation in Relativistic Systems

科罗拉多大学博尔德分校的Sandeep Sharma获得了化学学部化学理论、模型和计算方法（CTMC）项目的奖励，他开发了高精度的理论方法来预测含过渡金属体系的性质，这对技术具有至关重要的影响。它们的应用范围从催化缓慢的化学反应到展示可用于量子计算的不寻常的磁性。尽管过渡金属在技术上很重要，但计算其性质的理论方法远不如有机分子发达，有机分子可以进行高精度的计算，其精度可以与实验的精度相媲美。这一缺陷可以追溯到相关电子运动和相对论影响之间复杂的相互作用，这两者对过渡金属比有机分子重要得多。夏尔马博士正致力于通过开发一套治疗含金属系统的方法来填补这一空白。使用这些方法对过渡金属系统进行预测、准确的计算，可以指导设计高效、廉价的仿生催化剂的实验工作，也有助于设计下一代量子计算系统。夏尔马博士还在开发一门课程，以提高本科化学家的数学技能，这对年轻化学家来说是至关重要的。Sharma正在开发从头算方法，这种方法可以可靠地用于含有过渡金属的相对论系统，也显示出强烈的电子相关性。在过去的二十年里，在处理强电子相关性和大相对论效应的算法开发方面，很大程度上独立的团体取得了令人印象深刻的进展。然而，在平等的基础上同时对待它们仍然是一项艰巨的挑战。Sharma博士研究的一个主要目标是将这两个领域的最新思想进行富有成效的交叉融合，从而开发出能够处理强相关相对论系统的算法。更具体地说，他正在开发的方法：(i)计算包含重原子的小型基准系统的完全相对论四分量狄拉克-库仑-布雷特哈密顿量的基态和低洼激发态，这些系统是通过精确对角化无法达到的，接近精确的精度。实施近似精确对角化，作为一种主动空间方法，以获得一种定量准确的方法，用于处理生物和材料科学中感兴趣的大型系统。（iii）利用解析响应理论计算全从头算自旋哈密顿参数，以预测在实验和理论处理中广泛使用的参数。该奖项反映了美国国家科学基金会的法定使命，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，被认为值得支持。

Sandeep Sharma at the University of Colorado, Boulder is supported by an award from the Chemical Theory, Models and Computational Methods (CTMC) Program in the Chemistry Division to develop high accuracy theoretical methods to predict the properties of transition metal-containing systems, which have critically important technological impacts. Their applications range from catalyzing slow chemical reactions to exhibiting unusual magnetic properties that can used for quantum computing. Despite the technological importance of transition metals, theoretical methods to calculate their properties are much less developed than for organic molecules, where high-accuracy calculations can be performed that rival the accuracy of experiments. This shortcoming can be traced to the intricate interplay between correlated electronic motion and the impacts of relativity, both of which are much more important for transition metals than for organic molecules. Dr. Sharma is working to fill this void by developing a suite of methods to treat metal-containing systems. Predictive, accurate calculations on transition metal systems using these methods can direct experimental efforts in designing efficient and cheap biomimetic catalysts as well help design the next generation of systems for quantum computing. Dr. Sharma is also developing a course to improve the mathematical skills of undergraduate chemists, which is a critical need for young chemists.Dr. Sharma is developing ab initio methods that can reliably be used for transition metal-containing relativistic systems, that also display strong electron correlation. In the last two decades, impressive advances have been made by largely independent communities toward the development of algorithms to treat strong electron correlation and large relativistic effects. However, treating them simultaneously on an equal footing remains a formidable challenge. A major goal of Dr. Sharma's research is the fruitful cross-fertilization of the latest ideas in the two fields in order to develop algorithms that allow the treatment of strongly correlated relativistic systems. More specifically, he is developing methods that: (i) Calculate the ground and low-lying excited states of the fully relativistic four-component Dirac-Coulomb-Breit Hamiltonian for small benchmark systems containing heavy atoms, that are inaccessible by exact diagonalization, to near-exact accuracy. (ii) Implement near-exact diagonalization as an active space method to obtain a quantitatively accurate method for treating large systems of interest in biology and material science. (iii) Employ analytic response theory to calculate fully ab initio spin Hamiltonian parameters in order to predict parameters that are widely used in experiments and theoretical treatments.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.