In this paper, high-pressure data from a synchrotron X-ray diffraction study on a lillianite (Pb3Bi2S6) single crystal up to ~21 GPa are presented. A phase transition from lillianite (space group Bbmm, LP lillianite) to the high-pressure form β-Pb3Bi2S6 (space group Pbnm, HP lillianite) was confirmed and bracketed between 4.90 and 4.92 GPa. The transition is reversible but of first-order with a hysteresis of ~2.8 GPa. It showed weak effects of pseudo-merohedral twinning that disappeared upon decompression, testifying to a full recovery of the single crystal of lillianite. This makes lillianite an interesting shape-memory material.With a bulk modulus K4.9 = 78(3) GPa and K′ = 5.1(4), β-Pb3Bi2S6 is markedly less compressible than lillianite [K0 = 44(2) GPa, K′ = 7(1)]. Compressional anisotropy increases markedly in β-Pb3Bi2S6 with compressibility along the b axis [M0b = 130(6) GPa and Mb′ = 19(3) in lillianite, M4.9b = 145(4) GPa and Mb′ = 16.0(7) in β-Pb3Bi2S6] significantly larger than that along the other two axes [M0a = 118(5) GPa, Ma′ = 21(3), M0c = 139(12) GPa, and Mc′ = 31(10) in lillianite, M4.9a = 242(12) GPa, Ma′ = 8(1), M4.9c = 242(5) GPa, and Mc′ = 29(1) in β-Pb3Bi2S6].The behavior of lillianite at high pressure is an interesting case study in relation to non-quenchable ultrahigh-pressure phases likely occurring in the inner Earth, like post-perovskite MgSiO3, the oxide homologue N = 1 of the lillianite series. The β-Pb3Bi2S6 structure, on the other hand, is the N = 3 homologue of the meneghinite series to which the higher-pressure modification of the post-perovskite structure also belongs (homologue N = 1). This makes the two forms of Pb3Bi2S6 potential equivalents of high- and ultrahigh-pressure Mg silicates that could occur both in the deep earth and in other rocky extrasolar planetary bodies.

中文翻译：

---

莲石的高压单晶同步辐射X射线衍射研究

在本文中，提供了对高达 ~21 GPa 的百合石 (Pb3Bi2S6) 单晶进行同步加速器 X 射线衍射研究的高压数据。从 lillianite（空间群 Bbmm，LP lillianite）到高压形式 β-Pb3Bi2S6（空间群 Pbnm，HP lillianite）的相变得到确认，并在 4.90 和 4.92 GPa 之间括起来。这种转变是可逆的，但是是一阶的，滞后约为 2.8 GPa。它显示出在减压时消失的伪三面体孪晶的微弱影响，证明了百合石单晶的完全恢复。这使得 lillianite 成为一种有趣的形状记忆材料。体积模量 K4.9 = 78(3) GPa 和 K' = 5.1(4)，β-Pb3Bi2S6 的可压缩性明显低于 lillianite [K0 = 44(2) GPa， K' = 7(1)]。β-Pb3Bi2S6 的压缩各向异性显着增加，沿 b 轴的可压缩性 [M0b = 130(6) GPa 和 Mb' = 19(3) 在 lillianite 中，M4.9b = 145(4) GPa 和 Mb' = 16.0(7)在 β-Pb3Bi2S6 中] 明显大于沿其他两个轴的 [M0a = 118(5) GPa, Ma' = 21(3), M0c = 139(12) GPa, 和 Mc' = 31(10) in lillianite, M4.9a = 242(12) GPa, Ma' = 8(1), M4.9c = 242(5) GPa, and Mc' = 29(1) in β-Pb3Bi2S6]。一个有趣的案例研究与可能发生在地球内部的不可淬灭的超高压相有关，例如钙钛矿后的 MgSiO3，即百合石系列的氧化物同系物 N = 1。另一方面，β-Pb3Bi2S6 结构，是镁锰矿系列的 N = 3 同系物，后钙钛矿结构的高压改性也属于该系列（同系物 N = 1）。这使得两种形式的 Pb3Bi2S6 潜在等效于高压和超高压 Mg 硅酸盐，它们可能出现在地球深处和其他岩石系外行星体中。