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The chemistry of hypercoordination has been a subject of fundamental interest, especially for understanding structures that challenge conventional wisdom. The small ionic radii of Fe ions typically result in coordination numbers of 4 or 6 in stable Fe‐bearing ionic compounds. While 8‐coordinated Fe has been observed in highly compressed oxides, the pursuit of hypercoordinated Fe still faces significant challenges due to the complexity of synthesizing the anticipated compound with another suitable anion. Through first‐principles simulation and advanced crystal structure prediction methods, we predict that an orthorhombic phase of FeF3 with exclusively 8‐coordinated Fe is energetically stable above 18 GPa—a pressure more feasibly achieved compared to oxides. Inspired by this theoretical result, we conducted extensive experiments using a laser‐heated diamond anvil cell technique to investigate the crystal structures of FeF3 at high‐pressure conditions. We successfully synthesized the predicted orthorhombic phase of FeF3 at 46 GPa, as confirmed by in situ experimental X‐ray diffraction data. This work establishes a new ionic compound featuring rare 8‐coordinated Fe in a simple binary Fe‐bearing system and paves the way for discovering Fe hypercoordination in similar systems. [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]

• The Pt-H compounds were synthesized with the diamond anvil cell technique. • The experimental compression behavior of hcp PtH is determined above 100 GPa. • The structural relationship between PtH and SiH 4 is expounded directly. To date, the exact structure of PtH, the key to resolve the controversial hexagonal close-packed (hcp) phase of SiH 4 , is still absent above 100 GPa. Therefore, PtH has been synthesized and its compression behavior is determined through the angle dispersive X-ray diffraction method. We find that hcp PtH keeps stable up to at least 128 GPa and its experimental lattice parameters are highly consistent with those of the hcp one in the SiH 4 experiment. The present results provide reliable experimental information of PtH under high pressure, and directly clarify the debate between hcp PtH and "SiH 4 ". [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]

Using a diamond-anvil cell (DAC), we conducted in situ angle dispersive X-ray diffraction (ADXRD) up to 47.6 GPa at room temperature to evaluate the structural stability of α -As 2 Te 3 . A reversible structural transition was observed at between 17.4 and 36.3 GPa. The high-pressure structure is solved by a γ -Bi 2 Te 3 -type monoclinic phase ( C 2/ c , γ -As 2 Te 3 ). Reliable structural analyses, such as Rietveld refinement of the powder x-ray data, were provided, which show that the previously reported high-pressure β -As 2 Te 3 phase is not existed. It is worth mentioning that twice pressure-induced electron phase transitions were revealed in α -As 2 Te 3 at about 3 and 6 GPa, which cause the striking fluctuation in thermoelectric property at that pressures. [ABSTRACT FROM AUTHOR]

The stabilities and phase evolutions of the binary Bi–S compounds are investigated by using synchrotron radiation X-ray diffraction in a diamond anvil cell in combination with laser heating technique. When it is heated to 1300 K at 32.6 GPa, Bi 2 S 3 decomposes into element S and a new BiS phase, which can be quenched to ambient conditions. The present results verify that cubic BiS, with an unprecedented stoichiometry and novel bonding characteristics, is at least metastable. It may shed new light on the fundamental sciences and potential technologies of the group V-VI binary compounds. • The stabilities and phase evolutions of the binary Bi-S compounds under extreme conditions are investigated in detail. • Advanced synchrotron radiation X-ray diffraction in combination with laser heating technique is used. • Bi 2 S 3 is thermodynamically unstable and decompose into a novel phase with an unprecedented BiS stoichiometry. • The present results verify that cubic BiS, with an unprecedented stoichiometry, is at least metastable. [ABSTRACT FROM AUTHOR]