title: Quasi-harmonic approximation of thermodynamic properties of ice Ih, II, and III.
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.
authors.affiliation: Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain. ramirez@icmm.csic.es
authors.forename: R
authors.initials: R
authors.lastname: Ramírez
authors.forename: N
authors.initials: N
authors.lastname: Neuerburg
authors.forename: M-V
authors.initials: MV
authors.lastname: Fernández-Serra
authors.forename: C P
authors.initials: CP
authors.lastname: Herrero