Date of Award
Open Access Master's Thesis
Master of Science in Physics (MS)
Administrative Home Department
Department of Physics
Committee Member 1
Atmospheric scientists and climate modelers are faced with uncertainty around the process of ice production in clouds. While significant progress has been made in predicting homogeneous and heterogeneous ice nucleation rates as a function of temperature, recent experiments have shown that ice nucleation rates can be enhanced without decreasing temperature, through various mechanical agitations. One hypothesis for these findings is that mechanisms of stretching water and thereby inducing negative pressure in the liquid could lead to an increase in freezing rate. To better understand the viability of this concept, the effect of negative pressure on ice nucleation rates needs to be explored.
To that end, we have conducted molecular dynamics simulations of water at negative pressures. Homogeneous ice nucleation rates for the ML-mW and mW water models are evaluated at pressures ranging from atmospheric to -1000 atm, using Forward Flux Sampling and constant cooling simulations. We find that the density difference between ice and liquid water is central in determining the increase in nucleation rate with negative pressure. With these results, we analyze an equation that has been posed as a first order approximation to quantify how nucleation rate changes with negative pressure. The equation predicts the slope of lines of constant nucleation rate in temperature--pressure coordinates, shining a light on the importance of the water density anomaly in determining the slope. We conclude that this linear approximation works well for the mW and ML-mW water models and can be useful in making experimental predictions to advance the study of ice nucleation mechanisms.
Rosky, Elise, "Investigating ice nucleation at negative pressures using molecular dynamics: A first order approximation of the dependence of ice nucleation rate on pressure", Open Access Master's Thesis, Michigan Technological University, 2021.