The melting temperature of the six site potential model of water

Abascal, J. L. F.; Fernández, Ramón; Vega, Carlos; Carignano, Marcelo A.

doi:10.1063/1.2360276

Cited by 74 publications

(64 citation statements)

References 22 publications

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“…We note that the velocity of the solid-liquid interface depends strongly on the difference between the simulation temperature and the actual melting temperature (27). In the cases considered here, where we aimed at bracketing the melting temperature within 50-100 K, we expect to have interface velocities much larger than those observed in analogous calculations with empirical potentials, where the difference between simulation and melting temperatures are much smaller (28).…”

mentioning

confidence: 78%

Melting of ice under pressure

Schwegler

Sharma²,

Gygi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

123

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The melting of ice under pressure is investigated with a series of first-principles molecular dynamics simulations. In particular, a two-phase approach is used to determine the melting temperature of the ice-VII phase in the range of 10 -50 GPa. Our computed melting temperatures are consistent with existing diamond anvil cell experiments. We find that for pressures between 10 and 40 GPa, ice melts as a molecular solid. For pressures above Ϸ45 Gpa, there is a sharp increase in the slope of the melting curve because of the presence of molecular dissociation and proton diffusion in the solid before melting. The onset of significant proton diffusion in ice-VII as a function of increasing temperature is found to be gradual and bears many similarities to that of a type-II superionic solid.high pressure ͉ phase transitions ͉ water

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mentioning

confidence: 78%

Melting of ice under pressure

Schwegler

Sharma²,

Gygi

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

123

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“…Although the initial results for LJ and inverse twelve power were not very successful (probably due to the small size of the systems and to the short length of the runs), the method is becoming more popular in the last few years. In fact it has been applied to simple fluids [172,173,174,175,153,176], metals [177,178,179,180], silicon [181], ionic systems [182,183], hard dumbells [184], nitromethane [135] and water [108,109,185,186,187,188,189,190,191]. Two simulation boxes, having an equilibrated solid and liquid respectively, are joined along the z axis (the direction perpendicular to the plane of the interface).…”

Section: Direct Fluid-solid Coexistencementioning

confidence: 99%

Determination of phase diagrams via computer simulation: methodology and applications to water, electrolytes and proteins

Vega¹,

Sanz

Abascal

et al. 2008

J. Phys.: Condens. Matter

278

452

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Abstract. In this review we focus on the determination of phase diagrams by computer simulation with particular attention to the fluid-solid and solid-solid equilibria. The methodology to compute the free energy of solid phases will be discussed. In particular, the Einstein crystal and Einstein molecule methodologies are described in a comprehensive way. It is shown that both methodologies yield the same free energies and that free energies of solid phases present noticeable finite size effects. In fact this is the case for hard spheres in the solid phase. Finite size corrections can be introduced, although in an approximate way, to correct for the dependence of the free energy on the size of the system. The computation of free energies of solid phases can be extended to molecular fluids. The procedure to compute free energies of solid phases of water (ices) will be described in detail. The free energies of ices Ih, II, III, IV, V, VI, VII, VIII, IX, XI and XII will be presented for the SPC/E and TIP4P models of water. Initial coexistence points leading to the determination of the phase diagram of water for these two models will be provided. Other methods to estimate the melting point of a solid, as the direct fluid-solid coexistence or simulations of the free surface of the solid will be discussed. It will be shown that the melting points of ice Ih for several water models, obtained from free energy calculations, direct coexistence simulations and free surface simulations, agree within their statistical uncertainty. Phase diagram calculations can indeed help to improve potential models of molecular fluids. For instance, for water, the potential model TIP4P/2005 can be regarded as an improved version of TIP4P. Here we will review some recent work on the phase diagram of the simplest ionic model, the restricted primitive model. Although originally devised to describe ionic liquids, the model is becoming quite popular to describe the behaviour of charged colloids. Besides the possibility of obtaining fluid-solid equilibria for simple protein models will be discussed. In these primitive models, the protein is described by a spherical potential with certain anisotropic bonding sites (patchy sites).

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“…Some recent applications include the study of fluidsolid coexistence in simple fluids, 7-12 metals, [13][14][15][16] silicon, 17 ionic systems, 18 hard dumbells, 19 nitromethane, 20 and water. [21][22][23][24][25][26][27][28][29] These works share the approach to the calculation of the melting properties from the direct simulation of the inhomogeneous fluid-solid system, using either Monte Carlo ͑MC͒ or molecular dynamics ͑MD͒ schemes. Both simulation techniques are equally valid, although MD is the technique of choice if one is interested in dynamical properties, such as crystal-growth rate just to mention an example.…”

Section: Introductionmentioning

confidence: 99%

Determination of the melting point of hard spheres from direct coexistence simulation methods

Noya

Vega

Miguel

2008

The Journal of Chemical Physics

Self Cite

109

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We consider the computation of the coexistence pressure of the liquid-solid transition of a system of hard spheres from direct simulation of the inhomogeneous system formed from liquid and solid phases separated by an interface. Monte Carlo simulations of the interfacial system are performed in three different ensembles. In a first approach, a series of simulations is carried out in the isothermal-isobaric ensemble, where the solid is allowed to relax to its equilibrium crystalline structure, thus avoiding the appearance of artificial stress in the system. Here, the total volume of the system fluctuates due to changes in the three dimensions of the simulation box. In a second approach, we consider simulations of the inhomogeneous system in an isothermal-isobaric ensemble where the normal pressure, as well as the area of the ͑planar͒ fluid-solid interface, are kept constant. Now, the total volume of the system fluctuates due to changes in the longitudinal dimension of the simulation box. In both approaches, the coexistence pressure is estimated by monitoring the evolution of the density along several simulations carried out at different pressures. Both routes are seen to provide consistent values of the fluid-solid coexistence pressure, p = 11.54͑4͒k B T / 3 , which indicates that the error introduced by the use of the standard constant-pressure ensemble for this particular problem is small, provided the systems are sufficiently large. An additional simulation of the interfacial system is conducted in a canonical ensemble where the dimensions of the simulation box are allowed to change subject to the constraint that the total volume is kept fixed. In this approach, the coexistence pressure corresponds to the normal component of the pressure tensor, which can be computed as an appropriate ensemble average in a single simulation. This route yields a value of p = 11.54͑4͒k B T / 3 . We conclude that the results obtained for the coexistence pressure from direct simulations of the liquid and solid phases in coexistence using different ensembles are mutually consistent and are in excellent agreement with the values obtained from free energy calculations.

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The melting temperature of the six site potential model of water

Cited by 74 publications

References 22 publications

Melting of ice under pressure

Melting of ice under pressure

Determination of phase diagrams via computer simulation: methodology and applications to water, electrolytes and proteins

Determination of the melting point of hard spheres from direct coexistence simulation methods

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