The complete chloroplast genome of Tulipa gesneriana (Liliaceae) and its phylogenetic analysis.

The complete chloroplast genome sequence of Tulipa gesneriana L. was determined to investigate its phylogenetic position. This plastome is 151,958 base pairs (bp) in length, and comprises two inverted repeat (IRa and IRb) regions of 26,352 bp, a small single-copy region of 17,123 bp and a large single-copy region of 82,131 bp. The GC contents of the cp genome were 36.6%. In total, we annotated 126 genes including 81 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis based on nine chloroplast genomes indicates that T. gesneriana is closely related to T. iliensis and T. thianschanica.

Calibration of Manganin pressure gauge for diamond-anvil cells.

Pressure calibration for most diamond-anvil cell (DAC) experiments is mainly based on the ruby scale, which is key to implementing this powerful tool for high-pressure study. However, the ruby scale can often hardly be used for programmably controlled DAC devices, especially the piezoelectric-driving cells, where a continuous pressure calibration is required. In this work, we present an effective pressure gauge for DACs made of Manganin metal based on the four-probe resistivity measurements. Pressure dependence of its resistivity is well established and shows excellent linear relations in the 0-30 GPa pressure range with a slope of 23.4 (9) GPa for the first-cycle compression, in contrast to that of multiple-cycle compression and decompression having a nearly identical slope of 33.7 (4) GPa likely due to the strain effect. In addition, the such-established Manganin scale can be used for continuously monitoring the cell pressure of piezoelectric-driving DACs, and the reliability of this method is also verified by the fixed-point method with a Bi pressure standard. Realization of continuous pressure calibration for programmably controlled DACs would offer many opportunities for the study of dynamics, kinetics, and critical behaviors of pressure-induced phase transitions.

Pressure-driven switching of magnetism in layered CrCl3.

Layered transition-metal compounds with controllable magnetic behaviors provide many fascinating opportunities for the fabrication of high-performance magneto-electric and spintronic devices. The tuning of their electronic and magnetic properties is usually limited to the change of layer thickness, electrostatic doping, and the control of electric and magnetic fields. However, pressure has been rarely exploited as a control parameter for tailoring their magneto-electric properties. Here, we report a unique pressure-driven isostructural phase transition in layered CrCl3 accompanied by a simultaneous switching of magnetism from a ferromagnetic to an antiferromagnetic ordering. Our experiments, in combination with ab initio calculations, demonstrate that such a magnetic transition hinders the bandgap collapse under pressure, leading to an anomalous semiconductor-to-semiconductor transition. Our findings not only reveal the potential applications of this material in electronic and spintronic devices but also establish the basis for exploring unusual phase transitions in layered transition-metal compounds.

Phase transition induced strain in ZnO under high pressure.

Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. These findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.

Pressure calibration in solid pressure transmitting medium in large volume press.

The pressure limit in the large-volume-press (LVP) is increasing, but the in situ pressure calibration in LVP is still not a well resolved problem. The variation of the electrical resistance of the manganin with pressure in a hydrostatic condition is well known and is widely used in the pressure calibration in LVP. However, the hydrostatic pressure condition is hard to be maintained for the unavoidable solidification of the pressure transmitting medium (PTM) with pressure increasing. Moreover, our understanding about the relationship between pressure and manganin's resistance in a solid transmitting medium is still limited. Therefore, it is difficult to calibrate higher pressure using manganin. We measured the electrical resistance of manganin under pressure in pyrophyllite, MgO, and NaCl, respectively. The results show a linear relationship between the resistance and pressure in the same PTM with good reproducibility. In addition, the resistance-pressure relationships of manganin in different PTM are obviously different. So the resistance of manganin in a given solid PTM can be satisfactorily used as a pressure gauge only in the same PTM but cannot be used in other pressure media. Our results make it possible to calibrate higher pressure in a solid pressure transmitting medium in LVP.