Events in Physics

Calculating anharmonic vibrational properties of water ice

Quantum nuclear vibrations are important in many materials where they influence properties such as thermodynamic stability, thermal expansion, phase stability, isotope effects, etc. Vibrational anharmonicity often plays a key role in determining these properties not only at high temperatures and/or pressures, but also at ambient pressure and low temperatures. Water ice provides a good example of this. I will briefly introduce some recently developed methods for calculating anharmonic vibrations in (crystalline) solids and the resultant vibrational corrections to properties such as the electronic band gap. Results for hexagonal and cubic ice will be presented. In particular, I will explain why hexagonal rather than cubic ice is the thermodynamically stable form of ice at ambient pressure. I will then discuss how quantum nuclear vibrations change the electronic band
gap. I will conclude with a brief overview of further applications.