The local atomic distribution in tetragonal PZT.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Piezoelectricity in lead zirconate titanate (PZT) is crucial for device applications.
• Previous research often overlooked the impact of local atomic distribution on PZT's intrinsic piezoelectricity.

Purpose of the Study:

• To elucidate the intrinsic piezoelectricity of tetragonal PZT by focusing on local atomic distribution.
• To investigate the role of colour symmetry in determining PZT's piezoelectric properties.

Main Methods:

• Utilized density functional theory (DFT) for first-principles calculations of electronic, phononic structures, and piezoelectricity.
• Employed the supercell approach based on colour symmetry to analyze 22 distinct atomic distributions.
• Applied classical Monte Carlo methods to study macroscopic properties at the morphotropic phase boundary (MPB).

Main Results:

• Achieved high piezoelectric coefficients (d33) of 957 pm/V at x=0.5 and 893 pm/V at x=0.55.
• Identified significant disparities in phonon vibration modes linked to colour symmetry, with lower symmetry supercells exhibiting softer modes.
• Observed weakening and reorientation of covalent bonds in electronic structures, correlating with free energy flattening and high piezoelectricity.

Conclusions:

• Colour symmetry is an effective descriptor for local atomic distribution in PZT supercells.
• Soft phonon modes arising from colour symmetry breaking are a newly identified source of high piezoelectricity.
• This approach provides new perspectives for understanding domain walls and phase boundaries in PZT.