Melting temperature of ice Ih calculated from coexisting solid-liquid phases

Area of Science:

• Computational physics and chemistry
• Materials science
• Thermodynamics

Background:

• Accurate simulation of water's phase behavior is crucial for understanding its unique properties.
• Proton-disordered hexagonal ice I(h) is the most common form of ice under ambient conditions.
• Molecular dynamics simulations offer a powerful tool for investigating material properties at the molecular level.

Purpose of the Study:

• To compute the melting temperature of proton-disordered hexagonal ice I(h) at 1-bar pressure.
• To evaluate the performance of four different water models (TIP4P, TIP5P, TIP4P-Ew, TIP5P-Ew) in predicting ice melting.
• To compare simulation results with existing experimental and computational data.

Main Methods:

• Molecular-dynamics simulations were performed using the two-phase coexistence method.
• Constant pressure, particle number, and enthalpy (NPH) ensemble was employed.
• Four distinct water models were utilized: TIP4P, TIP5P, TIP4P-Ew, and TIP5P-Ew.

Main Results:

• The melting temperature for TIP4P ice I(h) was calculated as 229 ± 1 K.
• The melting temperature for TIP5P ice I(h) was calculated as 272.0 ± 0.6 K.
• For the Ewald-optimized models, TIP4P-Ew yielded T(m) = 257.0 ± 1.1 K, and TIP5P-Ew yielded T(m) = 253.9 ± 1.1 K.

Conclusions:

• The calculated melting temperatures for TIP4P and TIP5P models align with previous simulation studies.
• The TIP4P-Ew and TIP5P-Ew models provide alternative melting point predictions for hexagonal ice.
• This study highlights the impact of water model choice on simulated thermodynamic properties like melting temperature.