Communication: Dynamical and structural analyses of solid hydrogen under vapor pressure.

Area of Science:

• Condensed matter physics
• Quantum chemistry
• Materials science

Background:

• Nuclear quantum effects are crucial for understanding hydrogen's phase diagram.
• Previous studies have not fully characterized solid H2 under vapor pressure.

Purpose of the Study:

• To investigate the dynamical and structural properties of solid H2 under vapor pressure.
• To differentiate solid H2 under vapor pressure from liquid and high-pressure solid H2.

Main Methods:

• Utilized a recently developed quantum molecular dynamics simulation method.
• Analyzed lattice structures, phonon frequencies, molecular configurations, and vibrational spectra.

Main Results:

• Reproduced stable hexagonal close-packed lattice structures with accurate phonon frequencies.
• Identified a zigzag molecular configuration as the most stable, contrasting with the liquid's T-shape.
• Observed periodic angular distributions indicating restricted molecular rotation due to asymmetric potentials.
• Detected discrete jumps in librational and vibrational frequencies and bond length during structural rearrangements.

Conclusions:

• Solid H2 under vapor pressure exhibits distinct structural and dynamical characteristics compared to liquid and high-pressure phases.
• These findings provide valuable insights for monitoring thermodynamic states of condensed hydrogens.