Enhancing the formation of ionic defects to study the ice Ih/XI transition with molecular dynamics simulations

Ice Ih, the common form of ice in biosphere, contains proton disorder. Its proton-ordered counterpart, XI, is thermodynamically stable below 72 K. However, even this temperature formation XI kinetically hindered and experimentally it obtained by doping with KOH. Doping creates ionic defects that promote migration protons associated change configuration. In article, we mimic effect molecular dynamics simulations using a bias potential enhances defects. The recombination ions thus formed proceeds through fast hydroxide results jump along hydrogen bond loop. This provides physical expedite way to configuration, accelerate diffusion configuration space. A key ingredient approach machine learning trained density functional theory data capable modeling dissociation. We exemplify usefulness idea studying order-disorder transition an appropriate order parameter distinguish environments Ih XI. calculate changes free energy, enthalpy, entropy transition. Our estimated agrees experiment within error bars our calculation.