Hydrogen bond asymmetric local potentials in compressed ice.

Area of Science:

• Physical Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Hydrogen bonds are crucial in various materials, including ice.
• Understanding their behavior under extreme conditions like compression is vital.
• Previous studies lacked detailed insights into the local potentials of hydrogen bonds in compressed ice.

Purpose of the Study:

• To resolve the asymmetric, local, and short-range potentials of the hydrogen bond (O:H-O) in compressed ice.
• To analyze the atomic shifts and bond length changes under compression.
• To quantify the van der Waals and exchange potentials involved.

Main Methods:

• Utilized a combination of Lagrangian mechanics of oscillator vibrations.
• Employed molecular dynamics for decomposition of volume evolution.
• Applied Raman spectroscopy for phonon relaxation analysis.

Main Results:

• Observed outward shift of both oxygen atoms relative to hydrogen, increasing O-O distance by 0.0136 nm (0.2597 to 0.2733 nm) due to Coulomb repulsion.
• Noted subsequent inward movement of oxygen atoms along the O:H-O bond under compression, approaching an identical length of 0.11 nm.
• Determined the van der Waals potential (VL(r)) for the O:H bond reached -0.25 eV.
• Quantified the lowest exchange potential (VH(r)) for the H-O bond at -3.97 eV.

Conclusions:

• The study successfully resolved the complex potentials governing hydrogen bonds in compressed ice.
• Compression induces significant, asymmetric atomic shifts and modifies bond characteristics.
• The findings provide critical data on interatomic potentials in ice under pressure.