Efficient First-Principles Framework for Overdamped Phonon Dynamics and Anharmonic Electron-Phonon Coupling in...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Superionic conductors exhibit unique properties crucial for energy applications.
• Understanding local disorder and anharmonicity is key to optimizing their performance.
• Electron-phonon coupling significantly influences material properties.

Purpose of the Study:

• To introduce a novel ab initio quasistatic polymorphous framework for superionic conductors.
• To investigate the roles of local disorder, anharmonicity, and electron-phonon coupling.
• To elucidate the mechanisms behind the high figure of merit in these materials.

Main Methods:

• Utilizing an anharmonic special displacement method.
• Employing an ab initio quasistatic polymorphous framework.
• Generating a limited set of configurations for efficient calculations.

Main Results:

• Positional polymorphism causes breakdown of phonon quasiparticles and overdamped vibrations, while preserving transverse acoustic phonons.
• Electronic spectral functions are highly broadened, with band gap openings of 1.0 eV due to polymorphism.
• Anharmonic electron-phonon coupling leads to a temperature-dependent band gap narrowing.

Conclusions:

• The developed framework accurately describes complex phenomena in superionic conductors.
• Polymorphism and anharmonicity are critical factors governing the electronic and vibrational properties.
• This approach facilitates efficient computational studies of superionic crystals for materials discovery.