Code and Data for: Is Water a Mixture: Unsupervised Likelihood-Ratio Classification Reveals Two Water States That Merge Upon Increasing Temperature

Code and data accompanying the article "Is Water a Mixture: Unsupervised Likelihood-Ratio Classification Reveals Two Water States That Merge Upon Increasing Temperature".

Each water molecule is classified without supervision as a locally favored tetrahedral structure (LFTS), a disordered normal-liquid structure (DNLS), or transitional, using a likelihood ratio from a two-component Gaussian mixture over local order parameters, fitted once at TIP4P/2005, -20 C and then held fixed. The two groups are identified through their oxygen-oxygen structure factors, and the classifier is applied to TIP4P/2005, TIP5P and SWM4-NDP water from -30 to +90 C.

Contents:

• code_figures_tables.zip: simulation (OpenMM), order parameter, classification and structure factor code, plus scripts that reproduce all figures and SI tables (run_all.sh runs the full pipeline).
• data_TIP4P-2005.zip, data_TIP5P.zip, data_SWM4-NDP.zip: trajectories, order parameters and classification labels for each water model.
• README.md: setup and usage instructions.

Correspondence: Bilin Zhuang (bzhuang@g.hmc.edu).