Brillouin Scattering Studies of Glasses, Melts, and Aqueous Fluids

9305071低音在地球流体迁移的定性理解需要准确的粘弹性和流体的可压缩性值。 我们提出了一个实验和理论研究的弹性性能（压缩性），松弛性能（衰减，粘度），和状态方程的流体的地质重要性，特别是硅酸盐熔体和超临界水溶液。 这些属性的物理机制和数据简化方法在很大程度上是相同的两组材料，因为是实验数据要获得的每一个。 从这个意义上说，硅酸盐熔体和水溶液被包含在地质流体的单一研究中是自然和适当的。 具体来说，我们将使用布里渊光散射技术测量硅酸盐玻璃和熔体的可压缩性和粘度高达1600 oC。 实验将在干燥条件下和在H2O的存在下进行，以研究水对熔体的高T粘度和弹性的影响。 将在较低温度（T700 ℃）和高达10 GPa的高压下使用外部加热的金刚石对顶砧单元对含水流体进行类似的测量。 这些实验需要对布里渊频谱的线形进行全面分析。 虽然布里渊技术直接产生高频，非弛豫特性，但对线型的全面分析允许从测量中提取流体的低频，弛豫特性。 因此，我们可以研究所观察到的特性的频率依赖性。 此外，对于某些所研究的系统，我们将获得足够高的温度数据，从而直接获得弛豫性质。 分子动力学（MD）的流体性质的计算机模拟将被用来识别特定的原子机制与光散射光谱中显示的功能，并extrapolate测量范围之外的属性。 高频介电常数的含水流体也将获得从拟议的光学测量和MD模拟的结果在很宽的频率范围内进行比较。 这些研究将使更多的流体热力学和输运性质和流体-岩石相互作用的定量模型被构建。

9305071 Bass A qualitative understanding of fluid migration in the Earth requires accurate values of viscoelastic properties and the compressibility of fluids. We propose an experimental and theoretical study of the elastic properties (compressibility), relaxational properties (attenuation, viscosity), and the equation of state of fluids of geological importance, in particular, silicate melts and supercritical aqueous solutions. Physical mechanisms of these properties and data reduction methodologies are largely the same for both groups of materials, as is the experimental data to be obtained for each. In this sense, it is natural and appropriate for silicate melts and aqueous solutions to be encompasses in a single study of geological fluids. Specifically, we will measure the compressibility and viscosity of silicate glasses and melts up to 1600oC using the Brillouin light scattering technique. Experiments will be done under both dry conditions and in the presence of H2O in order to investigate the effect of water on the high T viscosity and elasticity of melts. Similar measurement on aqueous fluids will be made at lower temperatures (T700oC) and at high pressures up to 10 GPa using an externally heated diamond anvil cell. These experiments will require a full analysis of the lineshape of the Brillouin spectra. Although the Brillouin technique yields directly high frequency, unrelaxed properties, a full analysis of the lineshapes allows the low frequency, relaxed properties of the fluids to be extracted from the measurements. We can therefore investigate the frequency dependence of the observed properties. In addition, for some of the systems investigated we will obtain data sufficiently high temperature that the relaxed properties ar obtained directly. Molecular dynamics (MD) computer simulations of the fluid properties will be used to identify specific atomic mechanisms with the features displayed in the light scattering spectra, and to extrapol ate the properties beyond the range of measurements. High frequency dielectric permittivity of aqueous fluids will also be obtained from the proposed optical measurements and compared with results of MD simulations over a wide range of frequencies. These studies will allow more quantitative models of fluid thermodynamic and transport properties and fluid-rock interactions to be constructed.