An impact structure 1400 m in diameter, formed by a bolide impact, has been discovered on Baijifeng Mountain in Tonghua City in Northeast China’s Jilin province. The impact structure takes the form of a cirque-shaped depression on the top of the mountain and is located in a basement mainly composed of Proterozoic sandstone and Jurassic granite. A large number of rock fragments composed mainly of sandstone, with a small amount of granite, are distributed on the top of Baijifeng Mountain. Planar deformation features (PDFs) have been found in quartz in the rock and mineral clasts collected from the surface inside the depression. The forms of the PDFs indexed in the quartz include among others, {101̄3}, {101̄2}, and {101̄1}. The presence of these PDFs provides diagnostic evidence for shock metamorphism and the impact origin of the structure. The impact event took place after the Jurassic Period and probably much later.

A material described as lutetium–hydrogen–nitrogen (Lu-H-N in short) was recently claimed to have “near-ambient superconductivity” [Dasenbrock-Gammon et al., Nature 615, 244–250 (2023)]. If this result could be reproduced by other teams, it would be a major scientific breakthrough. Here, we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al. Our x-ray diffraction measurements indicate that the obtained sample contains three substances: the face-centered-cubic (FCC)-1 phase (Fm-3m) with lattice parameter a = 5.03 Å, the FCC-2 phase (Fm-3m) with a lattice parameter a = 4.755 Å, and Lu metal. The two FCC phases are identical to the those reported in the so-called near-ambient superconductor. However, we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity. We also use a laser heating technique to heat a sample to 1800 °C and find no superconductivity in the produced dark blue material below 6.5 GPa. In addition, both samples remain dark blue in color in the pressure range investigated.

Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensed matter. However, the only way to determine crystal structures of materials above 100 GPa, namely, X-ray diffraction (XRD), especially for low Z materials, remains nontrivial in the ultrahigh-pressure region, even with the availability of brilliant synchrotron X-ray sources. In this work, we perform a systematic study, choosing hydrogen (the lowest X-ray scatterer) as the subject, to understand how to better perform XRD measurements of low Z materials at multimegabar pressures. The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254 GPa at room temperature [C. Ji et al., Nature 573, 558–562 (2019)]. We present our discoveries and experiences with regard to several aspects of this work, namely, diamond anvil selection, sample configuration for ultrahigh-pressure XRD studies, XRD diagnostics for low Z materials, and related issues in data interpretation and pressure calibration. We believe that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures, eventually testing structural models of metallic hydrogen.

Metal halide perovskites (HPVs) have been greatly developed over the last decade, with various compositions, dimensionalities, and morphologies, leading to an emergence of high-performance photovoltaic and optoelectronic applications. Despite the tremendous progress made, challenges remain, which calls for a better understanding of the fundamental mechanisms. Pressure, a thermodynamic variable, provides a powerful tool to tune materials’ structures and properties. In combination with in situ characterization methods, high-pressure research could provide a better fundamental understanding. In this review, we summarize the recent studies of the dramatic, pressure-induced changes that occur in HPVs, particularly the enhanced and emergent properties induced under high pressure and their structure-property relationships. We first introduce the characteristics of HPVs and the basic knowledge of high-pressure techniques, as well as in situ characterization methods. We then discuss the effects of pressure on HPVs with different compositions, dimensionalities, and morphologies, and underline their common features and anomalous behaviors. In the last section, we highlight the main challenges and provide suggestions for possible future research on high-pressure HPVs.