Schaffrinna Tim, Milman Victor, Winkler Björn
Institute of Geosciences, Goethe University, Frankfurt, Germany.
Dassault Systèmes BIOVIA, Cambridge, UK.
Sci Rep. 2024 Feb 14;14(1):3760. doi: 10.1038/s41598-024-54088-8.
An atomistic pathway for a strain-induced subsolidus martensitic transition between quartz and coesite was found by computing the set of the smallest atomic displacements required to transform a quartz structure into a coesite structure. A minimal transformation cell with 24 [Formula: see text] formula units is sufficient to describe the diffusionless martensitic transition from quartz to coesite. We identified two families of invariant shear planes during the martensitic transition, near the {10[Formula: see text]1} and {12[Formula: see text]2} set of planes, in agreement with the orientation of planar defect structures observed in quartz samples which experienced hypervelocity impacts. We calculated the reaction barrier using density functional theory and found that the barrier of 150 meV/atom is pressure invariant from ambient pressure up to 5 GPa, while the mean principal stress limiting the stability of strained quartz is [Formula: see text] 2 GPa. The model calculations quantitatively confirm that coesite can be formed in strained quartz at pressures significantly below the hydrostatic equilibrium transition pressure.
通过计算将石英结构转变为柯石英结构所需的最小原子位移集，发现了一种应变诱导的石英与柯石英之间亚固相线马氏体转变的原子路径。一个包含24个[化学式：见原文]化学式单元的最小转变晶胞足以描述从石英到柯石英的无扩散马氏体转变。我们在马氏体转变过程中确定了两个不变切变面族，靠近{10[化学式：见原文]1}和{12[化学式：见原文]2}平面组，这与在经历超高速撞击的石英样品中观察到的平面缺陷结构的取向一致。我们使用密度泛函理论计算了反应势垒，发现150毫电子伏特/原子的势垒在从环境压力到5吉帕的压力范围内是不变的，而限制应变石英稳定性的平均主应力为[化学式：见原文]2吉帕。模型计算定量地证实了在远低于静水压力平衡转变压力的压力下，应变石英中可以形成柯石英。
