AI Article Synopsis
- The study investigates the thermodynamic properties of different ice phases (Ih, II, III) using a quasi-harmonic approximation, which is more computationally efficient than traditional methods.
- This approach allows for the analysis of important properties like volume, bulk modulus, and heat capacity while capturing quantum effects from atomic vibrations.
- Results indicate that the quasi-harmonic approximation closely matches classical and quantum simulations, especially at low temperatures, without losing accuracy under varying pressure conditions until close to mechanical stability limits.
Article Abstract
Several thermodynamic properties of ice Ih, II, and III are studied by a quasi-harmonic approximation and compared to results of quantum path integral and classical simulations. This approximation allows to obtain thermodynamic information at a fraction of the computational cost of standard simulation methods, and at the same time permits studying quantum effects related to zero-point vibrations of the atoms. Specifically, we have studied the crystal volume, bulk modulus, kinetic energy, enthalpy, and heat capacity of the three ice phases as a function of temperature and pressure. The flexible q-TIP4P/F model of water was employed for this study, although the results concerning the capability of the quasi-harmonic approximation are expected to be valid independently of the employed water model. The quasi-harmonic approximation reproduces with reasonable accuracy the results of quantum and classical simulations showing an improved agreement at low temperatures (T< 100 K). This agreement does not deteriorate as a function of pressure as long as it is not too close to the limit of mechanical stability of the ice phases.
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