Local-spin-density-approximation molecular-dynamics simulations of dense deuterium

Area of Science:

• Computational physics
• Materials science
• Quantum chemistry

Background:

• Deuterium exhibits complex behavior under extreme conditions.
• Understanding the molecular to dissociated transition is crucial for high-pressure physics.

Purpose of the Study:

• To investigate deuterium's molecular phase using local-spin-density-approximation molecular dynamics.
• To analyze the transition to the dissociated regime and its thermodynamic properties.

Main Methods:

• Local-spin-density-approximation (LSDA) molecular dynamics simulations.
• Focus on two deuterium isochores: V=6 cm³/mol and V=4 cm³/mol.

Main Results:

• The transition from molecular to dissociated deuterium shows negative isochoric curvature (ΔP/ΔT < 0).
• LSDA accurately describes the molecular phase, while local-density-approximation (LDA) is recovered in the dissociated regime.
• The observed negative curvature is insufficient to explain experimental compressibility data.

Conclusions:

• LSDA simulations provide insights into deuterium's phase transitions under pressure.
• Discrepancies with experimental compressibility suggest limitations in current theoretical models for this regime.