High-pressure structures of yttrium hydrides.

Area of Science:

• Condensed Matter Physics
• Materials Science
• High-Pressure Physics

Background:

• Yttrium hydrides (YH3 and YH4) are of interest for their potential superconducting properties.
• Understanding their structural and electronic behavior under extreme conditions is crucial for discovering new superconductors.

Purpose of the Study:

• To explore the crystal structures of YH3 and YH4 at high pressures (100-250 GPa).
• To investigate the electronic structures and phonon dispersion properties of these hydrides.
• To predict the superconducting transition temperatures (Tc) of different predicted structures.

Main Methods:

• Utilized a genetic algorithm combined with first-principles calculations.
• Investigated structural, electronic, and phonon properties at various pressures and temperatures.

Main Results:

• Predicted new crystal structures for YH3 with space group symmetries P21/m and I4/mmm.
• The P21/m structure of YH3 exhibits a superconducting transition temperature (Tc) of 19 K at 120 GPa, decreasing to 9 K at 200 GPa.
• The YH4 compound demonstrates significantly higher Tc values, reaching 94 K at 120 GPa and 55 K at 200 GPa.

Conclusions:

• New high-pressure phases of YH3 have been identified, with one phase showing moderate superconductivity.
• Yttrium tetrahydride (YH4) presents a promising candidate for high-temperature superconductivity under high pressure.
• These findings contribute to the ongoing search for novel superconducting materials.