Molecular dynamics with nuclear quantum effects: merging the quantum and classical domains

南卡罗来纳州大学的Sophya Garashchuk获得了化学系化学理论，模型和计算方法项目的奖项，以开发考虑分子和材料中原子核行为的理论和计算方法。 这项研究的动机是需要了解纳米材料和大分子结构。深入了解这些结构和材料如何与电子，电池和医疗设备等应用中的光，电流和热相互作用，需要能够跨越时间，空间和层次的几个数量级的理论和计算方法。Garashchuk教授的研究从最基本的层面开始，例如，通过检查质子。由于计算成本的原因，更高级的计算描述（量子计算）一次仅限于几个原子核，与更复杂，更大和更重的原子核的简单经典表示合并。原子模拟产生实验相关的属性，如反应速度或电荷和能量传输速率的预测。 这些参数对于开发更大分子系统的更先进模型是必要的。 对系统的特性和对外部刺激（温度、电场和磁场）的响应进行建模可以指导实验，并加速传感、计算、通信和其他应用的新材料和分子器件的开发。 Garashchuk教授的研究和教育活动将培养为新兴的量子信息科学做好准备的劳动力。 她促进使用计算化学和计算在教育和研究中的学生和研究人员在她的家机构，以及在姐妹校园和主要本科院校在整个南卡罗来纳州。该研究团队参与K-12科学演示，展示分子及其在日常技术中的作用。这些活动扩大了代表性不足的群体在研究中的参与，开发了下一代技术，并将STEM的贡献传达给了南卡罗来纳州的公众，这是全球研究企业中地理上代表性不足的群体。Garashchuk开发了适用于大型（10-1000个原子）分子系统的核分级处理的理论和计算方法。该层次结构由精确（依赖于时间的基础）和近似方法（经典动力学，可能与量子校正）统一的轨迹框架。精确的量子动力学采用高斯基，高斯基通过遵循遵循量子轨迹的概率密度流来适应演化的核波函数。这样的基函数演化定义了组态空间中的波函数的“最小化”表示，并提高了该方法随系统尺寸的缩放特性。高斯函数通过构造是相关的和可归一化的。 原子核的多级描述，有助于利用时间和质量尺度分离的有效的计算方法，接口上的飞行电子结构计算。采用量子轨道引导的自适应高斯（QTAG）动力学方法研究了分子聚集体中的核量子效应。e.晶体材料，酶催化循环的活性位点，共价键和金属有机骨架中的功能分子，作为调节和控制其与分子传感器、开关、催化剂的设计以及新兴的量子器件和计算机应用相关的性质的一种方式。将研究与教育和劳动力发展联系起来，Garashchuk将计算化学纳入研究生和本科生课程，为地区本科院校提供网络研究机会，用手，该奖项反映了NSF的法定使命，并被认为是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。

Sophya Garashchuk of the University of South Carolina 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 that consider the behavior of the nuclei in molecules and materials. This research is motivated by the need to understand nanomaterials and large molecular structures. In-depth understanding of how such structures and materials interact with light, current and heat in applications such as electronics, batteries and medical devices requires theoretical and computational methods capable of spanning several orders of magnitude in time, space, and hierarchy. Professor Garashchuk's research starts at the most fundamental level possible, for example, by examining protons. The more advanced computational descriptions (quantum calculations) that are restricted to just a few atomic nuclei at a time due to computational cost are merged with simpler classical representations for more complex, bigger and heavier nuclei. The atomistic simulations yield experimentally relevant properties such as predictions of the speed of the reaction or charge and energy transport rates. These parameters are necessary for the development of even more advanced models of bigger molecular systems. Modeling the systems’ properties and responses to external stimuli (temperature, electric and magnetic fields) guides the experiments and accelerate the development of new materials and molecular devices for sensing, computing, communications and other applications. Professor Garashchuk's research and educational activities will train the workforce ready for the emerging quantum information science. She promote use of computational chemistry and computing in education and research among students and researchers at her home institution, as well as at sister campuses and predominantly undergraduate institutions throughout the state of South Carolina. The research team is engaged in K-12 science demonstrations to showcase molecules and their roles in everyday technologies. These activities broaden participation of underrepresented groups in research, develop of the next-generation technologies, and communicate contributions of STEM to the general public of South Carolina, a geographically underrepresented group in the global research enterprise.Garashchuk develops theory and computational methods for the hierarchical treatment of nuclei practical for large (10-1000 atoms) molecular systems. The hierarchy consists of exact (time-dependent bases) and approximate methods (classical dynamics, possibly, with quantum corrections) unified by the trajectory framework. The exact quantum dynamics employs Gaussian bases which adapt to the evolving nuclear wave function by following the probability density flow, which follows the quantum trajectories. Such basis function evolution defines ‘minimalistic’ representation of a wavefunction in configuration space and improves the scaling properties of the method with the system size. The Gaussians are correlated and normalizable by construction. The multilevel description of the nuclei, helps to exploit the time- and mass-scale separation for an efficient computational methodology, interfaced with on-the-fly electronic structure calculations. The Quantum Trajectory-guided Adaptable Gaussian (QTAG) dynamics is employed to study nuclear quantum effects in molecular aggregates, i. e. crystalline materials, active sites of enzyme catalytic cycle, functional molecules integrated into covalent and metal-organic frameworks, as a way to tune and control their properties relevant to the design of molecular sensors, switches, catalysts, and to the emerging quantum device and computer applications. Connecting research with education and workforce development, Garashchuk incorporates computational chemistry into the graduate and undergraduate curriculum, by providing cyber-research opportunities to regional undergraduate colleges, and by hands-on training of students at all levels in computational chemistry tools and methods.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.