Anharmonic effects on the dynamics of solid aluminium fromab initiosimulations

Area of Science:

• Condensed matter physics
• Materials science
• Computational physics

Background:

• Accurate simulation of phonon properties in solids is crucial for understanding material behavior.
• Beyond the harmonic approximation, anharmonic effects significantly influence material properties at finite temperatures.
• Self-consistent ab initio lattice dynamics (SCAILD) and decoupled anharmonic mode approximation (DAMA) are advanced methods for capturing these effects.

Purpose of the Study:

• To critically benchmark SCAILD and DAMA against each other and molecular dynamics simulations.
• To compare simulation results with experimental data for face-centered cubic (fcc) aluminium.
• To investigate the temperature-dependence of phonon properties and atomic displacements.

Main Methods:

• Density-functional theory (DFT) for electronic structure calculations.
• Implementation and comparison of SCAILD and DAMA simulation approaches.
• Analysis of phonon dispersion, density-of-states, heat capacity, and mean atomic displacement.
• Validation against experimental data for fcc aluminium.

Main Results:

• Anharmonic contributions to phonon frequencies are negligible, but significantly influence heat capacity.
• Atomic mean-square displacements are strongly affected by anharmonicity.
• SCAILD and DAMA access a reduced phase space compared to molecular dynamics.
• DAMA results closely match experimental displacement amplitudes from Debye-Waller factor analysis.

Conclusions:

• SCAILD and DAMA provide reliable methods for simulating anharmonic phonon properties.
• Anharmonic effects are most pronounced in atomic displacements and heat capacity.
• DAMA offers a computationally efficient and accurate approach for predicting anharmonic effects relevant to experimental observations.