Liquid Water and Interfacial, Cubic, and Hexagonal Ice Classification through Eclipsed and Staggered Conformation Template Matching

Abstract

We propose a novel method based on template-matching for the recognition of liquid water, cubic ice (ice I c ), hexagonal ice (ice I h ), clathrate hydrates, as well as different interfacial structures in atomistic and coarse-grained simulations of water and ice. The two template matrices represent the staggered and eclipsed conformations which are the building blocks of hexagonal and cubic ice , as well as clathrate crystals.The algorithm is rotationally invariant and highly robust against imperfections in the ice structure, and its sensitivity for recognizing ice-like structures can be tuned for different applications. Unlike most other algorithms, it can discriminate between cubic-, hexagonal-, clathrate-, mixed-, and other interfacial ice types, and is therefore wellsuited to study complex systems and heterogeneous ice nucleation.

Atomistic and coarse-grained simulations reveal increased ice nucleation activity on silver iodide surfaces in slit and wedge geometries

“…We use the LICH-TEST algorithm (Roudsari et al, 2021) for the recognition of liquid water, cubic and hexagonal ice structures, and different interfacial structures. The LICH-TEST algorithm analyses the local structure around each water molecule by identifying the number of staggered and eclipsed conformations between two neighboring water molecules, based on a template matching approach.…”

Atomistic and coarse grained simulations reveal increased ice nucleation activity on silver iodide surfaces in slit and wedge geometries

“…Simulation data and input files can be made available upon reasonable request. The LICH-TEST algorithm (Roudsari et al, 2021) used to identify ice structures is openly available on GitHub: https://github.com/opakarin/lich-test.…”

“…Figure 5(a-f) shows the average time evolution of cubic and hexagonal ice growth in wedge systems with different angles. Ice structures were determined using the LICH-TEST algorithm (Roudsari et al, 2021). Variation between the 15 individual simulations for each angle was small compared to the large differences between different wedge angles.…”

“…where R is the nucleation rate and γ is a compressed delay fitting parameter. The induction times are determined by monitoring the size of the largest ice cluster in the systems using the LICH-TEST algorithm (Roudsari et al, 2021). The probability distributions P liq (t) for wedge systems with different angles using the TIP4P/Ice model are illustrated in Fig.…”

“…We determine the cubicity, i.e., the ratio of cubic ice to total amount of ice, for each wedge system simulation from the ice structure analysis using the LICH-TEST algorithm (Roudsari et al, 2021). In the growth of unconfined ice, stackingdisordered ice forms with random sequences of cubic and hexagonal ice, with cubicity between one-half and two-thirds (Hudait et al, 2016).…”