High-pressure structural stability in pseudo spin ladder compound CaCu₂O₃: a computational and experimental study.

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Calcium cuprates are technologically relevant materials.
• Understanding their structural response to pressure is crucial for applications.

Purpose of the Study:

• Investigate the structural behavior of CaCu2O3 under high pressure up to ~12 GPa.
• Determine the elastic properties and identify any phase transitions.

Main Methods:

• High-pressure synchrotron X-ray diffraction experiments.
• First-principles density functional theory (DFT) calculations.
• Rietveld refinement for structural analysis.

Main Results:

• Observed weakly off-stoichiometric composition with antisite Ca-Cu defects.
• Detected strong anisotropic elastic compression, primarily along the c-axis.
• Identified anomalous stiffening beyond 3-5 GPa, with a bulk modulus increasing from ~54 GPa to ~103 GPa.
• Observed microstructural rearrangement and changes in bond evolution.

Conclusions:

• The structural and microstructural changes indicate a second-order isosymmetric phase transition.
• Experimental and DFT results for the bulk modulus are in good agreement.
• The findings provide insights into the complex behavior of CaCu2O3 under pressure.