Pressure induced semimetal-to-metal transition and new structure of Ta2NiSe5 above 10GPa.

Previous studies of the transition metal chalcogenide Ta2NiSe5 has identified two phase transitions occurring between 0-10GPa, involving the excitonic insulator-to-semiconductor transition at 1GPa and the semiconductor-to-semimetal transition at 3GPa. However, there is still a lack of in-depth research on the changes in its physical properties changes above 10GPa. In this study, Ta2NiSe5 were investigated under high-pressure conditions using high-pressure X-ray diffraction and high-pressure X-ray absorption experiments. During the experimental process, a novel phase transition from the semimetal to the metal phase was observed between 10-60GPa, specifically between 10-14GPa, and the structure of the new phase was determined to be P21/m through first-principles calculations.Thistransition mechanism is attributed to the sliding of the weakly coupled layers of Ta2NiSe5 within the a-c plane, leading to changes in the crystal lattice constants and symmetry. This research fills a gap in the understanding of Ta2NiSe5's crystal structure under high pressure and contributes to the broader field of transition metal chalcogenides. .