How relativistic physics and exchange–correlation choices shape thermodynamic predictions in heavy metals.
Application sectors: Nuclear energy & radiation shielding, Electronics & materials engineering, Aerospace & high-pressure materials science.
Keywords: spin–orbit coupling, density functional theory, quasi-harmonic approximation, thermodynamics, lead.
Lead (Pb), a prototypical heavy metal, plays a crucial role in applications ranging from radiation shielding to electronics. Its electronic structure is strongly influenced by relativistic effects, particularly spin–orbit coupling (SOC), making it an ideal system to test how accurately modern computational methods can predict thermodynamic behavior.
This study addresses a key gap: how SOC and exchange–correlation (xc) functionals jointly influence thermodynamic properties within the quasi-harmonic approximation (QHA). Using both scalar relativistic (SR) and fully relativistic (FR) pseudopotentials, combined with LDA, PBE, and PBEsol functionals, the work evaluates a wide set of properties including phonon dispersions, thermal expansion, heat capacity, and elastic constants.
The main findings are threefold. First, SOC significantly alters phonon dispersions and improves the description of known anomalies, particularly transverse mode softening. However, this improvement is not systematic across all properties. Second, the contribution of electronic excitations to thermodynamic quantities is negligible, simplifying future modeling strategies. Third, no single xc functional consistently outperforms others—PBE, PBEsol, and LDA each show strengths depending on temperature and property.
Importantly, the influence of SOC diminishes under pressure but remains non-negligible, highlighting its persistent role in heavy element systems.
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Reference paper
“Thermodynamic properties of fcc lead: A scalar and fully relativistic first principle study”
B. Thakur, X. Gong, and A. Dal Corso, Comp. Materials Science 249, 113677 (2025)
https://doi.org/10.1016/j.commatsci.2025.113677