Brillouin Scattering Studies of Glasses, Melts, and Aqueous Fluids

[9305071]巴斯要对地球上的流体迁移有定性的了解，就需要精确地计算流体的粘弹性特性和可压缩性。我们提出了一个实验和理论研究的弹性性质（压缩性），松弛性质（衰减，粘度），和流体状态方程的地质重要性，特别是硅酸盐熔体和超临界水溶液。这些性质的物理机制和数据简化方法在两组材料中基本上是相同的，为每组材料获得的实验数据也是如此。从这个意义上说，把硅酸盐熔体和水溶液包括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高达1600℃的硅酸盐玻璃和熔体的可压缩性和粘度。实验将在干燥条件下和有水存在的情况下进行，以研究水对熔体高T粘度和弹性的影响。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砧细胞对含水流体进行类似的测量。这些实验需要对布里渊光谱的线形进行全面分析。尽管布里渊技术直接产生了高频、非松弛特性，但对线形的全面分析可以从测量中提取流体的低频、松弛特性。因此，我们可以研究观测到的特性的频率依赖性。此外，对于所研究的一些系统，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）流体性质的计算机模拟将用于识别特定的原子机制与光散射光谱中显示的特征，并推断超出测量范围的性质。本文还将从提出的光学测量中获得水流体的高频介电常数，并将其与广泛频率范围内的MD模拟结果进行比较。这些研究将允许建立更多的流体热力学和输运性质以及流体-岩石相互作用的定量模型。

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.