We report the synthesis, at 7 GPa and 923 K, and the thermoelastic characterization, up to 16 GPa and 850 K, of a single crystal of Mg-sursassite, Mg5Al5Si6O21(OH)7. In situ high-pressure and high-temperature single-crystal diffraction allowed the study of structural variation at non-ambient conditions and the determination of bulk elastic properties. The refined parameters of a second-order Birch-Murnaghan equation of state (BM-II EoS) are V0 = 446.02(1) Å3 and KT0 = 135.6(7) GPa. The thermal expansion coefficients of a Berman-type EoS are α0 = 3.14 (5) × 10−5 K−1, α1 = 2.50(16) × 10−8 K−2, and V0 = 445.94(3). For comparison, the P-V EoS is determined for a natural sursassite sample, ideally Mn4Al6Si6O22(OH)6. The refined parameters of BM-II EoS [V0 = 470.2(3) Å3, KT0 = 128(4) GPa] indicate that composition has a minimal effect on elastic properties. The similarity of density and bulk properties of Mg-sursassite if compared to olivine and other anhydrous mantle minerals suggests that this phase could be overseen by geophysical methods.

中文翻译：

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Mg-sursassite的热弹性参数及其在俯冲板片中作为水载体的相关性

我们报告了在 7 GPa 和 923 K 下的合成，以及高达 16 GPa 和 850 K 的 Mg-sursassite 单晶 Mg5Al5Si6O21(OH)7 的热弹性表征。原位高压和高温单晶衍射允许研究非环境条件下的结构变化和确定体积弹性特性。二阶 Birch-Murnaghan 状态方程 (BM-II EoS) 的精细参数为 V0 = 446.02(1) Å3 和 KT0 = 135.6(7) GPa。Berman 型 EoS 的热膨胀系数为 α0 = 3.14 (5) × 10−5 K−1, α1 = 2.50(16) × 10−8 K−2 和 V0 = 445.94(3)。为了进行比较，PV EoS 是针对天然硫铅矿样品测定的，理想情况下是 Mn4Al6Si6O22(OH)6。BM-II EoS 的细化参数 [V0 = 470.2(3) Å3, KT0 = 128(4) GPa] 表明成分对弹性性能的影响最小。如果与橄榄石和其他无水地幔矿物相比，Mg-sursassite 的密度和体积性质的相似性表明该阶段可以通过地球物理方法进行监督。