Physical Properties of Core and Deep Mantle Constituents

对地球固体内核的地震研究表明，内核具有弹性各向异性和非均匀性，并且内核各向异性的视轴可能与地幔不同。为了充分解释这些数据，需要关于横波在密集高压金属（特别是铁）中的传播的信息。对于大多数候选下地幔组分，体积模量作为压力的函数，可以很好地受到实验的约束；然而，对剪切模量的行为知之甚少。了解下地幔地震速度的径向和横向变化的努力受到剪切弹性常数对压力和温度依赖的剩余不确定性的限制。利用脉冲受激散射技术，可以在高压金刚石砧池中不透明样品表面与周围压力介质之间产生界面波。然后确定这些波的速度，它们对剪切弹性常数特别敏感。具体目标包括：(1)测定铁、铁合金和其他金属在高压下的全张拉弹性和热性能；(2)测定合成、多晶、下地幔相在超高压下的各向同性弹性剪切模量。

Brown 0106683 Seismic studies of Earth's solid inner core indicate that the inner core is elastically anisotropic and inhomogeneous, and that the apparent axis of inner core anisotropy may rotate differentially from Earth's mantle. In order to fully interpret these data, information is needed on shear wave propagation through dense, high-pressure metals, particularly iron. For most candidate lower mantle constituents the bulk moduli, as functions of pressure, are reasonably well constrained by experiment; less, however, is known about the behavior of the shear modulus. Efforts to understand both radial and lateral variation of seismic velocities in the lower mantle are limited by the remaining uncertainty in the pressure and temperature dependence of the shear elastic constants. Using the technique of Impulsive Stimulated Scattering, interfacial waves can be generated between the suface of an opaque sample in the high-pressure diamond-anvil cell and the surrounding pressure medium. The velocities of these waves, which are particularly sensitive to the shear elastic constants, are then determined. Specific goals include: (1) determination of full tensorial elastic and thermal properties of iron, iron alloys, and other metals at high pressures and (2) determination of isotropic elastic shear moduli at very high pressure of synthesized, polycrystalline, lower mantle phases.