Large-Scale Phonon Calculations Using the Real-Space Multigrid Method.

Area of Science:

• Materials Science
• Computational Physics
• Condensed Matter Physics

Background:

• Phonons are crucial for understanding material dynamics and thermal behavior.
• First-principles phonon calculations are computationally intensive, limiting system size.

Purpose of the Study:

• To implement and validate the finite displacement method (FDM) for phonon property calculations within the real-space multigrid (RMG) code suite.
• To assess the scalability and accuracy of RMG for large-scale electronic structure calculations.

Main Methods:

• Utilized the finite displacement method (FDM) with the highly parallel real-space multigrid (RMG) suite.
• Leveraged RMG's scalability across desktops, clusters, and supercomputers, including GPU support.
• Calculated the force constants matrix as the core computational step.

Main Results:

• Demonstrated high accuracy in force calculations at small atomic displacements.
• Achieved excellent agreement between RMG phonon band structures/vibrational spectra and established DFT codes (Quantum ESPRESSO, CASTEP, VASP).
• Validated results against inelastic neutron scattering experimental data from the VISION spectrometer.

Conclusions:

• RMG, coupled with FDM, provides an accurate and scalable computational tool for phonon property studies.
• The implementation is suitable for large-scale materials science research, bridging the gap between theory and experiment.