Topics in the Dynamics of Disordered Systems

非技术摘要：这项资助支持对无序材料性质的理论研究。将研究带电粒子(离子)在玻璃中的运动和氢在非晶硅中的运动。第一种物质现象可能会被用作计算机存储设备。第二种材料有很多应用，包括太阳能电池。所有级别的学生都将参与该项目，西班牙、英国和日本将继续进行国际合作。项目摘要这项研究提案旨在解决无序材料中的突出科学问题。其动机是需要了解玻璃中过渡金属离子的惊人快速动力学，以及氢化非晶硅中氢的成键和运动。在这两种情况下，都有非常重要的应用，这将受益于对材料的基本理解，特别是原子动力学。我们与领先的实验研究小组和亚利桑那州坦佩的一家成功的小公司密切合作。智慧价值玻璃中离子的动力学是一个持续感兴趣和重要的领域。我们研究了重掺银的GeSE玻璃的非晶相。银离子在这些材料中的运动对于传输的快速性是显著的。我们将阐明跳跃和陷阱的过程，这对这些系统中的驰豫理论是基本感兴趣的。这些玻璃是典型的固体电解质，并已被用于亚利桑那州Axon Technologies首创的极具前景的低功耗、非易失性计算机存储设备“可编程金属化单元”中。我们建议与该设备的发明者合作，发展对其操作的原子理解。以前的工作表明，合适的密度泛函方法可以真实地模拟这些材料的结构和动力学。氢化非晶硅是一种重要的电子材料，广泛应用于薄膜晶体管应用(如笔记本电脑显示器)，作为夜视设备的测辐射热材料，也是最重要的太阳能光伏材料之一。在实验基础上，H的运动已知决定了材料的关键属性，并与光诱导的亚稳性(Staebler-Wronski效应)有关。我们已经能够通过适当精确的第一性原理模拟和真实的结构模型来准确地跟踪氢的运动。与领先的实验小组合作，我们将使用最先进的第一性原理方法，在电子基态和模拟光激发状态下，确定H的动力学和光诱导亚稳态的原子起源。我们将用原子模拟的准确结果阐明当前的亚稳性模型。广泛影响上述基础研究的更广泛的影响是提供对新兴计算机存储设备的微观理解，以及一种重要的太阳能光伏材料的光诱导降解。我们将确保美国代表性不足的群体的参与(例如，两名在校学生是非洲人，我们最近毕业的学生是非洲人)。研究生、本科生和博士后的教育将继续是这项研究计划的首要任务。预计将与英国、西班牙和日本的研究人员进行国际合作。

Non-Technical Abstract: This grant supports theoretical research on the properties of disordered materials. Studies will be made of the motion of charged particles (ions) in glasses and on the motion of hydrogen in amorphous silicon. The first material phenomena could find application as a computer memory device. The second material has many applications including solar cells. Students at all levels will participate in the projects and international collaborations will be continued in Spain, Britain and Japan.Project SummaryThis research proposal aims to address outstanding scientific issues in disordered materials. The motivation arises from the need to understand the remarkably fast dynamics of transition metal ions in glasses and the bonding and motion of hydrogen in hydrogenated amorphous silicon. In both cases, there exist applications of great importance that will benefit from a fundamental understanding of the materials and especially the atomic dynamics. We work closely with leading experimental research groups and a successful small company in Tempe, Arizona.Intellectual MeritThe dynamics of ions in glasses is an area of sustained interest and importance. We studyamorphous phases of GeSe glasses heavily doped with Ag. The motion of the Ag ions in these materials is remarkable for rapidity of transport. We will elucidate the processes of hopping and trapping, of basic interest to the theory of relaxation in these systems. These glasses are prototypical solid electrolytes, and have been employed in the exceptionally promising "Programmable Metallization Cell" low power, non-volatile computer memory device pioneered by Axon Technologies of Arizona. We propose to work with the inventors of the device to develop an atomistic understanding of its operation. Previous work has shown that suitable density functional methods can faithfully model the structure and dynamics of these materials.Hydrogenated amorphous silicon is an important electronic material heavily used in thin film transistor applications (as for example in laptop displays), as a bolometric material for night vision devices, and is also one of the most important solar photovoltaic materials. On experimental grounds, the motion of H is known to determine key attributes of the material, and is associated with light-induced metastability (Staebler-Wronski effect). We have been able to accurately track the motion of hydrogen with suitably precise first principles simulations and realistic structural models. In collaboration with leading experimental groups, we will determine the dynamics of H and the atomistic origins of the light-induced metastability using state of the art first principles methods, both in the electronic ground state and in a simulated light-excited state. We will clarify current models of metastability with accurate results from atomisticsimulation.Broader ImpactThe broader impact of the fundamental research described above is to provide a microscopic understanding of an emerging computer memory device, and light-induced degradation of an important solar photovoltaic material. We will ensure the involvement of under-represented groups in the United States (for example, two current students are African, and our most recent graduate is African). Education of graduate students, undergraduates and post-docs will continue to be a top priority for this research program.International collaboration with researchers from Britain, Spain and Japan is anticipated.