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Nuclear quantum fluctuations in ice I(h)
Pedro Augusto Franco Pinheiro Moreira1, Maurice de Koning
1Departamento de Física, UFSCar, Rodovia Washington Luiz, km 235, CP 676, São Carlos-SP, 13565-905, Brazil. pmoreira@ufscar.br.
Physical Chemistry Chemical Physics : PCCP
|July 31, 2015
Summary
Nuclear quantum fluctuations significantly impact hydrogen-bond structure and molecular dipole moments in ice Ih. These fluctuations broaden and shift dipole distributions, affecting the dielectric properties of water ice.
Area of Science:
- Condensed Matter Physics
- Quantum Chemistry
- Materials Science
Background:
- Nuclear quantum fluctuations play a critical role in the properties of condensed matter systems.
- Understanding the behavior of protons in ice Ih is crucial for explaining its unique characteristics.
- Previous studies have explored hydrogen-bond structures and dipole moments, but the impact of quantum fluctuations requires further investigation.
Purpose of the Study:
- To investigate the influence of nuclear quantum fluctuations on the hydrogen-bond (HB) network and molecular dipole-moment distribution in ice Ih.
- To quantify the effects of quantum fluctuations on proton behavior and electronic density rearrangements.
- To correlate the observed changes with the dielectric properties of ice Ih.
Main Methods:
- Density Functional Theory (DFT)-based first-principles molecular dynamics (MD) simulations.
- Path-integral molecular dynamics (PIMD) simulations at a temperature of 100 K.
- Analysis of HB structure using parameters developed for liquid-phase molecular characterization.
- Computation of molecular dipole moments utilizing maximally localized Wannier functions.
Main Results:
- Protons in ice Ih exhibit substantial digressions due to quantum fluctuations, leading to significant electronic density rearrangements.
- Protonic quantum fluctuations broaden and shift the molecular dipole-moment distribution towards a larger mean value compared to simulations neglecting these effects.
- The enhanced mean dipole moment, when reconciled with experimental dielectric constant data (H2O vs. D2O ice), suggests sensitivity of the HB network topology to protonic quantum fluctuations.
Conclusions:
- Nuclear quantum fluctuations are a key factor in determining the molecular dipole-moment distribution and dielectric properties of ice Ih.
- The observed broadening and shift in dipole moments indicate a dynamic and quantum-influenced hydrogen-bond network.
- Further research into the interplay between quantum fluctuations and HB network topology is warranted for a comprehensive understanding of ice properties.
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