Computational Studies in Electrochemical Materials Science by Statistical-Mechanical and Ab-Initio Methods

[240078]这项资助支持一个研究表面电化学的理论项目。表面电化学在许多方面对社会福利做出了贡献，包括金属生产、电镀、防腐、能源储存、化学和制药工业的多相催化以及环境保护。尽管有这些多样化和经济上重要的应用，但只有在过去的二十年中，实验方法才允许在原子尺度上观察和操纵电极/电解质界面，而无需将电极移到超高真空环境中。这些新的纳米级原位方法包括扫描探针显微镜，如扫描隧道显微镜和原子力显微镜，以及使用高亮度同步加速器源的x射线衍射。这些新技术与传统的宏观电化学方法（如循环伏安法和计时库容法）相结合，开创了原子尺度电化学表面科学的新时代。因此，制造高科技材料和器件的电化学方法正在得到开发，这些材料和器件的性能来自纳米尺度的结构，并且有可能成为目前高真空技术的成本效益替代品。这些令人印象深刻的实验发展与计算机硬件和软件的惊人进步并行。十年前需要超级计算机才能完成的计算现在可以在个人计算机上完成，而今天最快的计算机和算法可以处理数十亿个原子。本研究将应用美国国家科学基金会最近支持的电化学材料科学动态现象的计算和理论研究的结果和技术来研究电化学吸附在单晶电极上的阴离子的动力学。这些结果和技术包括特定电化学系统的理论模型，高效的动态多尺度模拟算法和从头算量子力学方法。这些方法将进一步应用于研究电化学吸附在银和金上的卤化物，以及在快速脉冲电位下金表面的相变动力学。结果将与与实验组合作进行的实验进行比较。除了对特定系统的研究外，研究还将包括更广泛的工作，如吸附原子的扩散对吸附质结构的影响，在电极电位快速变化的条件下吸附质系统的动力学，以及在从头计算中包括电场影响和明确包括水分子的方法。研究人员还将继续开发模拟算法，以忠实地表示在小于10-10秒的原子时间尺度上发生的吸附、解吸和横向扩散的影响，同时能够在秒或更长时间尺度上模拟过程。桥接时间尺度的问题将以分层方式解决，使用小型连续体系统的研究来确定模拟中的输入参数，这些参数可以通过现代算法的应用达到宏观时间。这项研究有望提高对电极/电解质界面非平衡过程的理解，从而有助于开发新的、基于电化学的工艺来制造纳米颗粒、超薄膜和其他纳米结构材料。这项研究是让各个层次的学生参与发现过程的理想选择。这笔经费支持一个研究表面电化学的理论项目。表面电化学在许多方面对社会福利做出了贡献，包括金属生产、电镀、防腐、能源储存、化学和制药工业的多相催化以及环境保护。尽管有这些多样化和经济上重要的应用，但只有在过去的二十年中，实验方法才允许在原子尺度上观察和操纵电极/电解质界面，而无需将电极移到超高真空环境中。这些新的纳米级原位方法包括扫描探针显微镜，如扫描隧道显微镜和原子力显微镜，以及使用高亮度同步加速器源的x射线衍射。这些新技术与传统的宏观电化学方法（如循环伏安法和计时库容法）相结合，开创了原子尺度电化学表面科学的新时代。因此，制造高科技材料和器件的电化学方法正在得到开发，这些材料和器件的性能来自纳米尺度的结构，并且有可能成为目前高真空技术的成本效益替代品。这些令人印象深刻的实验发展与计算机硬件和软件的惊人进步并行。十年前需要超级计算机才能完成的计算现在可以在个人计算机上完成，而今天最快的计算机和算法可以处理数十亿个原子。本研究将应用美国国家科学基金会最近支持的电化学材料科学动态现象的计算和理论研究的结果和技术来研究电化学吸附在单晶电极上的阴离子的动力学。这些结果和技术包括特定电化学系统的理论模型，高效的动态多尺度模拟算法和从头算量子力学方法。这些方法将进一步应用于研究电化学吸附在银和金上的卤化物，以及在快速脉冲电位下金表面的相变动力学。结果将与与实验组合作进行的实验进行比较。除了对特定系统的研究外，研究还将包括更广泛的工作，如吸附原子的扩散对吸附质结构的影响，在电极电位快速变化的条件下吸附质系统的动力学，以及在从头计算中包括电场影响和明确包括水分子的方法。研究人员还将继续开发模拟算法，以忠实地表示在小于10-10秒的原子时间尺度上发生的吸附、解吸和横向扩散的影响，同时能够在秒或更长时间尺度上模拟过程。桥接时间尺度的问题将以分层方式解决，使用小型连续体系统的研究来确定模拟中的输入参数，这些参数可以通过现代算法的应用达到宏观时间。这项研究有望提高对电极/电解质界面非平衡过程的理解，从而有助于开发新的、基于电化学的工艺来制造纳米颗粒、超薄膜和其他纳米结构材料。这项研究非常适合让各个层次的学生参与发现过程

0240078RikvoldThis grant supports a theoretical project investigating surface electrochemistry. Surface electrochemistry contributes to the welfare of society in many ways, including metal production, electroplating, corrosion protection, energy storage, and heterogeneous catalysis for the chemical and pharmaceutical industries and environmental protection. Despite these diverse and economically important applications, it is only in the last two decades that experimental methods have become available that permit observation and manipulation of electrode/electrolyte interfaces on an atomic scale without removing the electrode to an ultra-high vacuum environment. These new, nanoscopic in situ methods include scanning probe microscopies, such as scanning tunneling microscopy and atomic force microscopy, and X-ray diffraction using high-brilliance synchrotron sources. In combination with the traditional, macroscopic methods of electrochemistry, such as cyclic voltammetry and chronocoulometry, these new techniques have ushered in a new era of atomic-scale electrochemical surface science. As a consequence, electrochemical methods to manufacture high-tech materials and devices that derive their properties from structure on the nanometer scale are being developed and have the potential to become cost-effective alternatives to current high-vacuum techniques. These impressive experimental developments are paralleled by spectacular progress in computer hardware and software. Calculations that required supercomputers a decade ago are now performed on personal computers, while today's fastest computers and algorithms can handle billions of atoms.This research will apply results and techniques from recent NSF-supported computational and theoretical studies of dynamical phenomena in electrochemical materials science to study the dynamics of anions that are electrochemically adsorbed on single-crystal electrodes. These results and techniques include theoretical models for specific electrochemical systems, highly efficient dynamic multiscale simulation algorithms, and ab initio quantum mechanical methods. The methods will be used and developed further in investigations of halides electrochemically adsorbed on silver and gold, and the dynamics of phase transformations of gold surfaces under rapidly pulsed potential. The results will be compared with experiments in collaboration with experimental groups. In addition to studies of specific systems, the research will include work of more general scope on effects of diffusion of adsorbed atoms on the adsorbate structure, on dynamics of adsorbate systems under conditions of rapidly varying electrode potentials, and on methods to include the effects of electric fields and to explicitly include water molecules in ab initio calculations.Work will also continue to develop simulation algorithms that faithfully represent the effects of adsorption, desorption, and lateral diffusion that occur on atomic time scales of less that 10-10 seconds, while enabling simulation of processes on a scale of seconds or longer. This problem of bridging time scales will be addressed in a hierarchical manner, using studies of small continuum systems to determine parameters for input in simulations that can reach macroscopic times with the application of modern algorithms.This research is expected to result in improved understanding of nonequilibrium processes at electrode/electrolyte interfaces, and thereby contribute to the development of new, electrochemistry-based processes to manufacture nanoparticles, ultrathin films, and other nanostructured materials. The research is ideal for involving students at all levels in the discovery process.%%%This grant supports a theoretical project investigating surface electrochemistry. Surface electrochemistry contributes to the welfare of society in many ways, including metal production, electroplating, corrosion protection, energy storage, and heterogeneous catalysis for the chemical and pharmaceutical industries and environmental protection. Despite these diverse and economically important applications, it is only in the last two decades that experimental methods have become available that permit observation and manipulation of electrode/electrolyte interfaces on an atomic scale without removing the electrode to an ultra-high vacuum environment. These new, nanoscopic in situ methods include scanning probe microscopies, such as scanning tunneling microscopy and atomic force microscopy, and X-ray diffraction using high-brilliance synchrotron sources. In combination with the traditional, macroscopic methods of electrochemistry, such as cyclic voltammetry and chronocoulometry, these new techniques have ushered in a new era of atomic-scale electrochemical surface science. As a consequence, electrochemical methods to manufacture high-tech materials and devices that derive their properties from structure on the nanometer scale are being developed and have the potential to become cost-effective alternatives to current high-vacuum techniques. These impressive experimental developments are paralleled by spectacular progress in computer hardware and software. Calculations that required supercomputers a decade ago are now performed on personal computers, while today's fastest computers and algorithms can handle billions of atoms.This research will apply results and techniques from recent NSF-supported computational and theoretical studies of dynamical phenomena in electrochemical materials science to study the dynamics of anions that are electrochemically adsorbed on single-crystal electrodes. These results and techniques include theoretical models for specific electrochemical systems, highly efficient dynamic multiscale simulation algorithms, and ab initio quantum mechanical methods. The methods will be used and developed further in investigations of halides electrochemically adsorbed on silver and gold, and the dynamics of phase transformations of gold surfaces under rapidly pulsed potential. The results will be compared with experiments in collaboration with experimental groups. In addition to studies of specific systems, the research will include work of more general scope on effects of diffusion of adsorbed atoms on the adsorbate structure, on dynamics of adsorbate systems under conditions of rapidly varying electrode potentials, and on methods to include the effects of electric fields and to explicitly include water molecules in ab initio calculations.Work will also continue to develop simulation algorithms that faithfully represent the effects of adsorption, desorption, and lateral diffusion that occur on atomic time scales of less that 10-10 seconds, while enabling simulation of processes on a scale of seconds or longer. This problem of bridging time scales will be addressed in a hierarchical manner, using studies of small continuum systems to determine parameters for input in simulations that can reach macroscopic times with the application of modern algorithms.This research is expected to result in improved understanding of nonequilibrium processes at electrode/electrolyte interfaces, and thereby contribute to the development of new, electrochemistry-based processes to manufacture nanoparticles, ultrathin films, and other nanostructured materials. The research is ideal for involving students at all levels in the discovery process.***