Phase changes and rheological properties of Earth and planetary materials under high-pressure and high-temperature

阐明了1998~2000年两年间重要地球和行星材料在高压高温下的相关系、结构和物理性质、相变和流变性。每年举行一次会议，介绍和讨论上述主题的成果，并相互交流。澄清的结果如下：1)在石榴石-钙钛矿转变过程中，硅酸盐钙钛矿中的Al随着压力和温度的升高而增加，并发现了新的高压铝硅酸盐相(Fujino)。2)确定了新的六方相MgAl_2O_4-CaAl_2O_4的晶体结构(Fujino)。3)在冲击陨石中发现了天然硅酸盐钛铁矿和钙钛矿。4)发现了一种新的高压相，并确定了它的稳定场。5)通过高压高温原位X射线观察(Irifune)确定了镁铝硅中尖晶石与钙钛矿+方镁石的相界。6)在高达27 Gpa的玄武岩和橄榄岩成分的高压实验中，K在过渡带和下地幔条件下转变为相容的元素(Takahashi)。7)通过原位X射线观察和电子衍射研究(Ohtani)，阐明了Mg_2SiO_4中α-β转变和伽马相分解的动力学(Ohtani)。9)通过分子动力学模拟(Matsui)高精度地再现了晶型为Mg2SiO4的晶体结构和物理性质。10)发展了一个时间分辨的新系统来分析相变(Yamanaka)。11)可以推导出描述生长固溶体晶体组成的基本方程(Kitamura)。

Phase relations, structures and physical properties, phase transformations and rheological properties of important Earth and planetary materials under high-pressure and high-temperature were clarified in these 2 years from 1998 to 2000. In each year, a meeting was held to present and discuss the results of the above subjects, and communicate with each other. The clarified results are as follows;1) In the garnet-perovskite transformation, Al in silicate perovskite increases with pressure and temperature, and a new high-pressure aluminous silicate phase was found (Fujino).2) The crystal structure of a new hexagonal phase in MgAl2O4-CaAl2O4 was determined (Fujino).3) Natural silicate ilmenite and perovskite were discovered in a shocked meteorite, and their formation mechanism was clarified (Fujino).4) A new high-pressure phase was found and its stability field was determined in MgAl2O4-CaAl2O4 (Akaogi).5) The phase boundary between spinel and perovskite+periclase in Mg2SiO4 was determined by the high-pressure and high-temperature in situ X-ray observation (Irifune).6) In the high-pressure experiments of the basalt and peridotite compositions up to 27 GPa, K changed to a compatible element under the transition-zone and lower mantle conditions (Takahashi).7) Kinetics of the alpha-beta transition and the decomposition of the gamma phase in Mg2SiO4 were clarified by the in situ X-ray observations and electron diffraction studies (Ohtani).8) The crystal structure of alpha-CaSi2O5 synthesized at 1500 C, 10 GPa was determined, and 5-coordinated Si was found (Kudoh).9) Crystal structures and physical properties of Mg2SiO4 polymorphs could be reproduced in high precision by the molecular dynamics simulation (Matsui).10) A time-resolved new system to analyze phase transitions was developed using a diamond anvil cell with a heater (Yamanaka).11) A basic equation to describe the composition of a growing solid solution crystal could be derived (Kitamura).