Molecular dynamics simulations of liquid methanol and methanol–water mixtures with polarizable models

Abstract

A polarizable model for simulation of liquid methanol, compatible with the COS/G2 water model, has been developed using the Charge-on-Spring (COS) technique. The model consists of three point charges, with one polarizable center on the oxygen atom. The Lennard-Jones parameters on the oxygen atom together with the molecular polarizability were varied to reproduce the experimental heat of vaporization and density of liquid methanol at ambient conditions. We examined the energies of various methanol dimers in the gas phase and compared them with values obtained from ab initio calculations. The model was then used to study the thermodynamic, dynamic, structural, and dielectric properties of liquid methanol as well as of a methanol-water mixture. A microscopic picture of the structure of pure liquid methanol and of the methanol-water mixture is provided. Good agreement was found between the results from our model simulations and available experimental and ab initio calculation data. In particular, the experimental dielectric permittivity of 32 could be reproduced, which had been shown to be difficult when using nonpolarizable models.

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

“…The RDFs of methanol have been determined experimentally [8][9][10][11] and have been computed by means of full ab initio MD, 5,[12][13][14][15] mixed empirical and ab initio interactions 16,17 and force-fields. [18][19][20][21][22][23][24][25][26] Often, the first intermolecular peak in the RDF of methanol as well of water is overestimated compared to experiment. 12,13,[15][16][17][23][24][25][27][28][29][30] The search for plausible explanations of this quasi systematic overestimation forms the onset of a long debate, but until now it is not yet unraveled and what suits for one particular case does not suit for another case.…”

“…[18][19][20][21][22][23][24][25][26] Often, the first intermolecular peak in the RDF of methanol as well of water is overestimated compared to experiment. 12,13,[15][16][17][23][24][25][27][28][29][30] The search for plausible explanations of this quasi systematic overestimation forms the onset of a long debate, but until now it is not yet unraveled and what suits for one particular case does not suit for another case. When computing RDFs from molecular simulations based on first principles (e.g.…”

Polarizable Empirical Force Field for the Primary and Secondary Alcohol Series Based on the Classical Drude Model

“…In other models parameters for hydroxyl groups are set to be unique for the particular alcohol being studied and can not be regarded as transferable across the alcohol series. [21][22][23] In the present work we extend these efforts via the development of a polarizable model for the alcohol series ( Figure 1) with emphasis on maximizing the transferability of the developed parameters to biological macromolecules. In addition, a systematic, iterative approach is applied to rigorously optimize all aspects of the force field parameters to maximize the overall accuracy of the model.…”

Liquid methanol Monte Carlo simulations with a refined potential which includes polarizability, nonadditivity, and intramolecular relaxation

“…[35][36][37][38]66 Furthermore, in two of these works 35,38 there was a comparison between the results produced by the potentials with and without polarization, indicating the need of polarization, even if some overstructuring could be occurring. 36,38 In the present model it is possible to turn off some molecular properties while keeping the same force field parameters, henceforth making the elucidation of the need of such property independent of a change in potential. Keeping the mobile charges fixed at certain positions would freeze a particular charge distribution, hence, for instance, its dipole, and then a nonpolarizable potential can be used.…”

“…Kashtanov et al 31 have suggested that numerical simulations could be using potentials that are not able to reproduce the hydrogen bonding network in ring structures. There is a substantial number of numerical simulations of methanol [18][19][20][21][22][23][32][33][34] and some of them which include polarizability [35][36][37][38] have shown the need for refined potentials.…”