High Pressure Brillouin Scattering Study of Incommensurate Systems

9310222 Hochheimer该项目采用独特的高压和布里渊光散射技术来研究晶格动力学，弹性行为和相变材料表现出无公度相。 正在调查的材料包括硒酸盐和卤化物，并已被选为模型系统，应提供测试最近的理论无公度相变。 这项研究将提供一个更好的理解耦合的声学声子激发在无公度相，并将提供额外的信息的作用，非谐晶格势的相位行为。 这些研究将提供有关固体相变的基本信息，这些信息在许多实际材料如铁电固体中是重要的。 这是一项关于压力对固体中原子排列的影响的基础研究，可以显示固体中原子位置的不寻常的长范围（大于晶体晶胞）调制。 相变的原因和所研究的材料中原子的原子位置的变化还没有很好的理解。 它们是重要的，并且是其他固体中相行为的基础，例如具有技术重要性的铁电材料。 原子位置的变化将用X射线和光谱技术进行研究。 ***

9310222 Hochheimer This project employs unique high pressure and Brillouin light scattering techniques to investigate lattice dynamics, elastic behavior and phase transitions in materials exhibiting incommensurate phases. The materials being investigated include selenates and halides and have been chosen as model systems which should provide tests of recent theories of incommensurate phase transitions. The research will provide a better understanding of the coupling of acoustic phonons to excitations in the incommensurate phase, and will provide additional information about the role of anharmonic lattice potentials in the phase behavior. The research will provide fundamental information about solid state phase transitions which are important in many practical materials such as ferroelectric solids. %%% This is a fundamental study of the effect of pressure on the arrangement of atoms in solids that can show an unusual long range (larger that the crystal unit cell) modulation of the atomic positions in the solids. The reasons for phase transitions and changes in the atomic positions of the atoms in the materials under study are not well understood. They are important and underlie phase behavior in other solids, such as ferroelectric materials of technological importance. The changes in atomic positions will be investigated with both x-ray and optical spectroscopy techniques. ***