First-Principles Molecular Dynamics in Metal-Halide Perovskites: Contrasting Generalized Gradient Approximation and...

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Physics

Background:

• Metal-halide perovskites (MHPs) are crucial for optoelectronics.
• First-principles molecular dynamics (FPMD) is vital for understanding MHP dynamics.
• Generalized gradient approximation (GGA) functionals offer efficiency but lack accuracy for MHPs, while hybrid functionals provide accuracy at a higher computational cost.

Purpose of the Study:

• To investigate the accuracy of the hybrid PBE0 functional for FPMD simulations of CsPbI3.
• To compare PBE0 results with GGA functionals regarding structural, electronic, and dynamical properties.
• To elucidate anharmonic effects and octahedral tilting instabilities in CsPbI3.

Main Methods:

• First-principles molecular dynamics (FPMD) simulations.
• Utilized the hybrid PBE0 functional for calculations.
• Compared results with generalized gradient approximation (GGA) functionals.

Main Results:

• PBE0 functional achieved excellent agreement with experimental data for lattice parameters and phonon modes.
• GGA functionals overestimated lattice parameters and band gaps, and underestimated phonon energies.
• FPMD simulations revealed lowered free energy barriers and farther separated potential wells for octahedral tilting with PBE0, indicating reduced anharmonicity.

Conclusions:

• Hybrid functionals, specifically PBE0, are essential for accurate FPMD simulations of metal-halide perovskites.
• Accurate modeling of crystal structure, lattice dynamics, and anharmonicity requires hybrid functionals.
• This study highlights the limitations of GGA functionals for precise MHP property prediction.