A transferable molecular model for accurate thermodynamic studies of water in large-scale systems

Due to its anomalies, water, essential in biological systems and various applications, poses a unique computational challenge. While diverse models have been proposed to simulate water efficiently, accurately reproducing its behavior across a broad range of temperatures and pressures for large-scale systems still remains elusive. To fill this gap, we develop a molecular model that balances accuracy, analytical tractability, and computational efficiency. By detailing hydrogen bond networks and many-body interactions while coarse-graining atomic coordinates via a density field, we establish a model calibrated against experiments at ambient conditions. It matches water's equation of state and response functions over a temperature range of approximately 60 degrees at atmospheric pressure and about 40 degrees up to 50 MPa. Our findings advance water property understanding, enabling precise thermodynamic calculations, including free energy, in systems with tens of millions of molecules, paving the way for exploration in various scientific disciplines.