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The structural evolution of lone-pair compounds under high-pressure and high-temperature conditions has been a subject of fundamental interest in revealing modulated polymorphs. As one of the archetypal lone-pair compounds, selenium dioxide (SeO2) has attracted much attention due to the pressure modulation of its one-dimensional infinite W-shaped chain arrangement. Here, through swarm intelligence algorithm in conjunction with the first-principles simulation, we propose the existence of an orthorhombic Pnma-SeO2 structure, characterized by V-shaped chains interconnected via vertex-sharing SeO3 pyramids. These V-shaped chains demonstrate reduced compressibility along their chain direction compared to the W-shaped chains. Calculations indicate that Pnma-SeO2 is a semiconductor with a large indirect bandgap of 2.39 eV. Remarkably, we synthesized the predicted Pnma-SeO2 in a laser-heated diamond anvil cell at a pressure of 48.5 or 87 GPa as identified by in situ synchrotron x-ray diffraction data. Our findings lead to a significant extension of the phase diagram and transition path of SeO2 and provide key insights into understanding the pressure modulation in lone-pair compounds. [ABSTRACT FROM AUTHOR]

Layered trihalides have attracted significant interest due to their potential applications in optical and spintronic devices. Herein, we report a combined experimental and theoretical investigation of antimony tribromide (SbBr3) under high pressure (up to 30 GPa) using synchrotron x-ray diffraction, Raman spectroscopy, alternating current (AC) impedance measurements, and first-principles calculations. The results indicate that SbBr3 transforms from a molecular phase (space group Pbnm) to an eight-coordinated layered phase (space group P21/a) at 7.6 GPa. A partial density of states analysis reveals that the eight-coordinated layered geometry of SbBr3 is rooted in the electron transfer from the Sb p orbital to the Br p orbital. Furthermore, based on AC impedance measurements, the resistance decreases with increasing pressure due to the gradual narrowing of the bandgap of SbBr3 in the Pbnm phase. The positive resistance–pressure relationship in the P21/a phase is attributed to the low carrier mobility caused by lattice distortion. Our current findings not only provide information on the phase diagram and electronic transport of SbBr3 but also expand the realm of layered functional materials in molecular trihalides. [ABSTRACT FROM AUTHOR]

Lithium metavanadate (LiVO3) is a typical ionic conductor with a monoclinic pyroxene-type structure at ambient conditions. Here, we investigated the structural and electrical transport properties of LiVO3 under high pressures by combining in situ Raman scattering, x-ray diffraction, impedance spectroscopy measurements, and first-principles calculations. All experimental and theoretical results demonstrated that LiVO3 undergoes a structural transition from monoclinic to triclinic phase at around 5 GPa, during which partial VO4 tetrahedrons are transformed into a VO6 octahedron. The ion migration of LiVO3 was significantly suppressed above 5 GPa and an ionic–electronic transition was discovered at 10.7 GPa. The structural evolution involving coordination environment change results in an electron density rearrangement around Li and O atoms, which are responsible for the transformation of electrical transport mechanism in LiVO3 under high pressures. These results expand our understanding of the electrical and structural properties of LiVO3 under high pressures and provide insights into the pressure effects on ion migration in solid electrolytes. [ABSTRACT FROM AUTHOR]

Combining alternate-current impedance spectrum measurement and first-principle calculations, we thoroughly analyzed the electrical transport behavior of LaAlO3 under high pressure. A pressure-induced ionic–polaronic–ionic transition has been discovered through impedance spectroscopy measurements. Through first-principle calculations, we have elucidated the physical origin of the emergence of polaronic conduction, which results from the distortion of electron density background around Al and O atoms. Furthermore, the discontinuous changes in the starting frequency of ion migration f W , relaxation frequency f b , and ionic resistance R i have been found at around 13.2 GPa, which can be ascribed to the phase transition of LaAlO3 from rhombohedral to cubic phase. Pressure can enhance the migration of O2− ions, causing an increase in the ionic conductivity of LaAlO3. This research will deepen our comprehension on the ion migration in solid electrolytes. [ABSTRACT FROM AUTHOR]

Combining alternate-current impedance spectrum measurement and first-principle calculations, we thoroughly analyzed the electrical transport behavior of LaAlO3 under high pressure. A pressure-induced ionic–polaronic–ionic transition has been discovered through impedance spectroscopy measurements. Through first-principle calculations, we have elucidated the physical origin of the emergence of polaronic conduction, which results from the distortion of electron density background around Al and O atoms. Furthermore, the discontinuous changes in the starting frequency of ion migration f W , relaxation frequency f b , and ionic resistance R i have been found at around 13.2 GPa, which can be ascribed to the phase transition of LaAlO3 from rhombohedral to cubic phase. Pressure can enhance the migration of O2− ions, causing an increase in the ionic conductivity of LaAlO3. This research will deepen our comprehension on the ion migration in solid electrolytes. [ABSTRACT FROM AUTHOR]

The structural evolution of lone-pair compounds under high-pressure and high-temperature conditions has been a subject of fundamental interest in revealing modulated polymorphs. As one of the archetypal lone-pair compounds, selenium dioxide (SeO2) has attracted much attention due to the pressure modulation of its one-dimensional infinite W-shaped chain arrangement. Here, through swarm intelligence algorithm in conjunction with the first-principles simulation, we propose the existence of an orthorhombic Pnma-SeO2 structure, characterized by V-shaped chains interconnected via vertex-sharing SeO3 pyramids. These V-shaped chains demonstrate reduced compressibility along their chain direction compared to the W-shaped chains. Calculations indicate that Pnma-SeO2 is a semiconductor with a large indirect bandgap of 2.39 eV. Remarkably, we synthesized the predicted Pnma-SeO2 in a laser-heated diamond anvil cell at a pressure of 48.5 or 87 GPa as identified by in situ synchrotron x-ray diffraction data. Our findings lead to a significant extension of the phase diagram and transition path of SeO2 and provide key insights into understanding the pressure modulation in lone-pair compounds. [ABSTRACT FROM AUTHOR]

Lithium metavanadate (LiVO3) is a typical ionic conductor with a monoclinic pyroxene-type structure at ambient conditions. Here, we investigated the structural and electrical transport properties of LiVO3 under high pressures by combining in situ Raman scattering, x-ray diffraction, impedance spectroscopy measurements, and first-principles calculations. All experimental and theoretical results demonstrated that LiVO3 undergoes a structural transition from monoclinic to triclinic phase at around 5 GPa, during which partial VO4 tetrahedrons are transformed into a VO6 octahedron. The ion migration of LiVO3 was significantly suppressed above 5 GPa and an ionic–electronic transition was discovered at 10.7 GPa. The structural evolution involving coordination environment change results in an electron density rearrangement around Li and O atoms, which are responsible for the transformation of electrical transport mechanism in LiVO3 under high pressures. These results expand our understanding of the electrical and structural properties of LiVO3 under high pressures and provide insights into the pressure effects on ion migration in solid electrolytes. [ABSTRACT FROM AUTHOR]