Bu Kejun, Luo Hui, Guo Songhao, Li Mei, Wang Dong, Dong Hongliang, Ding Yang, Yang Wenge, Lü Xujie
Center for High Pressure Science and Technology Advanced Research (HPSTAR), 1690 Cailun Road, Shanghai 201203, P. R. China.
J Phys Chem Lett. 2020 Nov 19;11(22):9702-9707. doi: 10.1021/acs.jpclett.0c02893. Epub 2020 Nov 2.
Lone-pair electrons (LPEs) s in subvalent 14 and 15 groups lead to highly anharmonic lattice and strong distortion polarization, which are responsible for the groups' outstanding thermoelectric and optoelectronic properties. However, their dynamic stereochemical role in structural and physical properties is still unclear. Here, by introducing pressure to tune the behavior of LPEs, we systematically investigate the lone-pair stereochemical role in a BiOS. The gradually suppressed LPEs during compression show a nonlinear repulsive electrostatic force, resulting in two anisotropic structural transitions. An orthorhombic-to-tetragonal phase transition happens at 6.4 GPa, caused by the dynamic cation centering. This structural transformation effectively modulates the optoelectronic properties. Further compression beyond 13.2 GPa induces a 2D-to-3D structural transition due to the disappearance of the Bi-6s LPEs. Therefore, the pressure-induced LPE reconfiguration dominates these anomalous variations of lattice, electronic, and optical properties. Our findings provide new insights into the materials optimization by regulating the characters of LPEs.
亚价态14族和15族中的孤对电子（LPEs）会导致高度非谐晶格和强烈的畸变极化，这是这些族具有出色热电和光电性能的原因。然而，它们在结构和物理性质中的动态立体化学作用仍不清楚。在此，通过引入压力来调节LPEs的行为，我们系统地研究了BiOS中孤对电子的立体化学作用。压缩过程中逐渐被抑制的LPEs表现出非线性排斥静电力，导致两个各向异性的结构转变。6.4 GPa时发生由动态阳离子居中引起的正交相到四方相的转变。这种结构转变有效地调节了光电性能。超过13.2 GPa的进一步压缩由于Bi-6s LPEs的消失而诱导二维到三维的结构转变。因此，压力诱导的LPEs重新配置主导了晶格、电子和光学性质的这些异常变化。我们的发现为通过调节LPEs的特性进行材料优化提供了新的见解。
