Quantum effects on the maximum in density of water as described by the TIP4PQ/2005 model

Abstract

Path integral simulations have been performed to determine the temperature of the maximum in density of water of the rigid, nonpolarizable TIP4PQ/2005 model treating long range Coulombic forces with the reaction field method. A maximum in density is found at 280 K, just 3 K above the experimental value. In tritiated water the maximum occurs at a temperature about 12 K higher than in water, in reasonable agreement with the experimental result. Contrary to the usual assumption that the maximum in classical water is about 14 K above that in water, we found that for TIP4PQ/2005 this maximum is about 30 K above. For rigid water models the internal energy and the temperature of maximum density do not follow a linear behavior when plotted as a function of the inverse of the hydrogen mass. In addition, it is shown that, when used with Ewald sums, the TIP4PQ/2005 reproduces quite nicely not only the maximum in density of water, but also the liquid densities, the structure of liquid water and the vaporization enthalpy. It was shown in a previous work that it also reproduces reasonably well the density and relative stabilities of ices. Therefore the TIP4PQ/2005 model, while still simple, allows one to analyze the interplay between quantum effects related to atomic masses and intermolecular forces in water.

Analysis of the basis set superposition error in molecular dynamics of hydrogen-bonded liquids: Application to methanol

“…34 A general feature is that nuclear quantum effects make the structure of the liquid water softer. [35][36][37][38][39][40] One notices a broadening and lowering of the RDF compared to the distribution generated from classical molecular dynamics simulations. 34,[41][42][43] An alternative is the Car-Parrinello molecular dynamics method, 44 which is based on the description of the intermolecular interactions at the density functional level of theory.…”

Quantum effects of hydrogen atoms on the dynamical rearrangement of hydrogen-bond networks in liquid water

“…Computer simulation has been a strategy of particular importance in this field. The path-integral Monte Carlo ͑PIMC͒ method was used to assess the effect of quantum-mechanical fluctuations on the liquid structure, [14][15][16][17][18] and the centroid MD ͑CMD͒, ring polymer MD, and semiclassical initial value representation methods were proposed to study the water dynamics through equilibrium correlation functions and meansquare displacement. [1][2][3][4][5][6][7][8] The classical MD is nowadays very straightforward and is routinely used to study complex chemical problems involving many thousands of particles.…”

Path integral Monte Carlo simulations for rigid rotors and their application to water

“…For the system sizes studied in this work (N=300-360) the reaction field technique yielded slightly higher energies and densities than the Ewald summations, but the location of the TMD was unchanged 46 .…”

“…This can be explained because classical models are usually fitted to reproduce some experimental data at room temperature, so in some way quantum effects at this temperature are implicit in the model. For example, it has been found that the structure of liquid water and ices I h and II above 250K is reproduced with similar accuracy in classical and quantum simulations (although only quantum simulations can reproduce isotopic effects) 46 . The densities of ices can also be reproduced at room temperature with good accuracy using classical simulations 45 .…”