Molecular Simulation of Silicate Melts: Structure-Property Relations and the Influence of Volatiles

硅酸盐熔体的分子模拟：结构-性能关系和挥发物的影响

• 批准号: 0635820
• 负责人: James Van Orman
• 金额: $ 21.98万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-01 至 2010-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635820&HistoricalAwards=false
• 关键词: Molecular; Simulation; Silicate; Melts; Structure

Diffusion plays a critical role in many important mantle processes, including chemical exchange, solid-state creep, seismic attenuation and electrical conduction. This study will provide experimental data on cation and oxygen diffusion rates in the two most abundant lower mantle minerals, perovskite (MgSiO3) and periclase (MgO). High-pressure, high-temperature experiments on both minerals will be performed under well-defined thermochemical conditions, with point defect concentrations controlled by the addition of aliovalent cations. In periclase, diffusion coefficients for oxygen and a broad range of monovalent, divalent and trivalent cations will be determined at pressures between 1 atm and 25 GPa and temperatures of 1200-2300 K. An important goal of these experiments is to determine quantitative relationships between diffusivity and ionic parameters such as radius, charge and polarizability. Experiments on perovskite will focus on Mg and O self-diffusion at 25 GPa and 1700-2300 K. The study is designed to gain a fundamental understanding of the mechanisms for ionic transport in perovskite and periclase, and the influence of temperature, pressure and composition on diffusivity.

扩散在许多重要的地幔过程中起着关键作用，包括化学交换、固态蠕变、地震衰减和导电。 这项研究将提供实验数据的阳离子和氧的扩散速率在两个最丰富的下地幔矿物，钙钛矿（MgSiO 3）和方镁石（MgO）。 在定义明确的热化学条件下，对两种矿物进行高压，高温实验，通过添加异价阳离子控制点缺陷浓度。 在方镁石中，氧和宽范围的一价、二价和三价阳离子的扩散系数将在1大气压和25 GPa之间的压力和1200-2300 K的温度下测定。 这些实验的一个重要目标是确定扩散率和离子参数（如半径、电荷和极化率）之间的定量关系。 钙钛矿的实验将集中在25 GPa和1700-2300 K下的Mg和O自扩散。 这项研究的目的是获得钙钛矿和方镁石的离子传输机制的基本理解，以及温度，压力和成分对扩散率的影响。