Evolution of Hydrogen Dynamics in Amorphous Ice with Density

Area of Science:

• Condensed matter physics
• Materials science
• Physical chemistry

Background:

• Amorphous ices are technologically relevant materials.
• Understanding single-particle dynamics is crucial for characterizing material properties.
• Hydrogen bonding significantly influences the behavior of amorphous ices.

Purpose of the Study:

• To investigate the single-particle dynamics of hydrogen atoms in amorphous ices.
• To determine the effect of density on hydrogen kinetic energy and bonding.
• To compare the capabilities of DINS, INS, and Raman spectroscopy for probing O-H stretching modes.

Main Methods:

• Deep inelastic neutron scattering (DINS)
• Inelastic neutron scattering (INS)
• Analysis of hydrogen kinetic energies and vibrational potentials

Main Results:

• Mean kinetic energies of hydrogen nuclei increase with density.
• Increasing density weakens hydrogen bonds and leads to more harmonic potentials.
• DINS reveals more significant changes in O-H stretching kinetic energy than INS or Raman spectroscopy.
• Anharmonicity constants for O-H stretching modes were determined.

Conclusions:

• DINS is a powerful technique for accurate ground-state kinetic energy determination beyond the harmonic approximation.
• The study provides benchmark kinetic energy data for path-integral Monte Carlo simulations.
• Density plays a critical role in modifying hydrogen bonding and dynamics in amorphous ices.