Ground-State Crystal Structure of Strontium Peroxide Predicted from First Principles

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Strontium peroxide (SrO2) is a typical alkaline earth metal peroxide.
• The CaC2-type structure (I4/mmm) was widely believed to be the stable ambient structure for SrO2.

Purpose of the Study:

• To investigate the stable structure of SrO2 at ambient and high-pressure conditions.
• To explore the energetic favorability of different SrO2 crystal structures.

Main Methods:

• First-principles swarm structure searching simulations.
• Frozen-phonon calculations.
• Electronic band structure calculations.

Main Results:

• A monoclinic structure (C2c) is predicted to be energetically more favorable than the CaC2-type structure at ambient pressure and low temperature.
• The CaC2-type structure (I4/mmm) is stable only at high pressures (>20 GPa) or elevated temperatures.
• A high-pressure phase (P21/c) with two layers of peroxide ions was identified above 36 GPa.
• All stable SrO2 structures exhibit wide band gap semiconductor properties.

Conclusions:

• The stable structure of SrO2 at ambient conditions is likely monoclinic (C2c), not tetrahedral (I4/mmm).
• Pressure and temperature significantly influence the crystal structure of SrO2.
• This study advances the understanding of alkaline earth metal peroxide structures and properties.