Structure and Electronic Anomalies of Amorphous Chalcogenides

无定形硫属化物的结构和电子异常

• 批准号: 1465125
• 负责人: Vassiliy Lubchenko
• 金额: $ 43.2万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1465125&HistoricalAwards=false
• 关键词: Structure; Electronic; Anomalies; Amorphous; Chalcogenides

Vassiliy Lubchenko of the University of Houston is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to develop a theoretical and computational approach to studying an important class of inorganic solids, called the "chalcogenides," that contain elements from groups XVI (sulfur, selenium, tellurium), XV (phosphorus, arsenic, antimony, bismuth), and XIV (germanium). The ability of these solids to switch readily between ordered crystalline and amorphous ("glassy") forms allows one to tune the optical and electronic properties of these materials in an efficient way. This property makes the chalcogenides prime candidates for applications in optical drives, next generation computer memory and displays, smart optics, and novel computer architectures Amorphous chalcogenides are a special type of disordered solids called "glasses," which are ordinarily made by rapidly cooling a liquid, usually below its melting point One can convert a chalcogenide alloy between the glass and ordered crystalline form by first melting the material and, then, cooling the melt at a specified rate. Slow cooling yields the crystal, fast cooling yields the glass. The present study is establishing detailed connections between the molecular motions underlying the glass transition and quantum-chemical interactions in the chalcogenide alloys. Direct molecular modeling of the glass transition is difficult and is part of the greater challenge of predicting the structure of complex inorganic solids and designing materials with tailored properties. The study is exploiting the similarity of the interplay between distinct chemical interactions in the chalcogenides and the behavior of a well-defined model of mathematical physics to make the problem tractable. At the center of the broader impact activities is training of graduate, undergraduate, and, in particular, high school students. A strategy is in place to ensure the participating high school and undergraduate students complete meaningful subprojects that will contribute to peer-reviewed publications.The microscopic hypothesis of the proposed work is that the glass-forming ability of the chalcogenide alloys stems from a competition between distinct types of chemical bonding: covalent, multicenter, and secondary. The resulting complex interplay of interactions is captured by a classic model of statistical physics, viz., the 64-vertex model, which is being implemented. The most important outputs of the calculation are the structure and the configurational entropy of amorphous chalcogenides. The configurational entropy determines the complexity of the free energy landscape of the alloys and their glass-forming ability. To back up these calculations, a novel procedure is being implemented for generating dense glassy structures for particles with distorted-octahedral bonding typical of the chalcogenides. An additional coarse-graining description is being implemented with the help of a recently developed 6-component spin model based on the theory of elasticity of structurally-degenerate solids.

休斯顿大学的Vassiliy Lubchenko获得了化学系化学理论，模型和计算方法项目的奖项，以开发一种理论和计算方法来研究一类重要的无机固体，称为“硫属化物”，含有第XVI族元素（硫，硒，碲），XV族元素（磷，砷，锑，铋）和XIV族元素（锗）。 这些固体在有序晶体和非晶（“玻璃态”）形式之间容易切换的能力允许人们以有效的方式调节这些材料的光学和电子性质。 这种性质使得硫属化物在光学驱动器、下一代计算机存储器和显示器、智能光学和新型计算机架构中的应用成为主要候选者。非晶硫属化物是一种特殊类型的无序固体，称为“玻璃”，通常通过快速冷却液体（通常低于其熔点）来制备 人们可以通过首先熔化材料，然后以特定速率冷却熔体，在玻璃和有序晶体形式之间转换硫属化物合金。 缓慢冷却产生晶体，快速冷却产生玻璃。 目前的研究是建立详细的分子运动之间的联系，玻璃化转变和硫系合金中的量子化学相互作用。 玻璃化转变的直接分子建模是困难的，并且是预测复杂无机固体的结构和设计具有定制特性的材料的更大挑战的一部分。 这项研究利用了硫属化物中不同化学相互作用之间的相互作用的相似性，以及一个定义明确的数学物理模型的行为，使问题变得易于处理。 在更广泛的影响活动的中心是研究生，本科生，特别是高中生的培训。 一个战略是到位，以确保参与高中和本科生完成有意义的子项目，将有助于同行评议publication.The微观假设的拟议工作是玻璃形成能力的硫属合金源于不同类型的化学键之间的竞争：共价键，多中心，和二级。 由此产生的相互作用的复杂相互作用是由一个经典的统计物理模型，即，64顶点模型，正在实施中。 计算的最重要的输出是非晶硫属化物的结构和组态熵。 组态熵决定了合金自由能谱的复杂性及其玻璃形成能力。 为了支持这些计算，正在实施一种新的程序，用于产生致密的玻璃结构的颗粒与扭曲的八面体键合典型的硫属化物。 一个额外的粗粒化描述正在实施的帮助下，最近开发的6个组成部分的自旋模型的基础上，结构退化固体的弹性理论。