Structure and dynamics in aqueous mixtures of glycerol: insights from molecular dynamics simulations.

Aqueous glycerol mixtures are investigated over the whole concentration range of glycerol = 0.1-0.9 molecular dynamics (MD) simulations at ambient pressure and temperature.

The influence of charge ordering in the microscopic structure of monohydroxy alcohols.

While radiation scattering data provides insight inside the microstructure of liquids, the Debye relation relating the scattering intensity() to the atom-atom structure factorsSab(k)shows that, ultimately, it is these individual structure correlation functions which contain the relevant information about the micro-structure. However, these quantities are not observables, except in few cases where one can invert the Debye relation to obtain the structure functions. In the majority of other cases, the need for model dependent computer simulations is unavoidable.

Reply to the 'Comment on "Universal features in the lifetime distribution of clusters in hydrogen-bonding liquids"' by J. Grelska, , 2024, , https://doi.org/10.1039/D3CP05269A.

In this reply, we discuss some aspects of the comments in , 2024, , https://doi.org/10.1039/D3CP05269A, by Grelska, about our work , 2021, , 19537.

Role of Charge Ordering in the Dynamics of Cluster Formation in Associated Liquids.

Liquids are archetypes of disordered systems, yet liquids of polar molecules are locally more ordered than nonpolar molecules, due to the Coulomb interaction based charge ordering phenomenon. Hydrogen bonded liquids, such as water or alcohols, for example, represent a special type of polar liquids, in that they form labile clustered local structures. For water, in particular, hydrogen bonding and the related local tetrahedrality, play an important role in the various attempts to understand this liquid.

Lifetime distribution of clusters in binary mixtures involving hydrogen bonding liquids.

Hydrogen bonded liquids are associated liquids and tend to exhibit local inhomogeneity in the form of clusters and segregated sub-nano domains. It is an open question as to whether Hbonded clusters in pure water have common features with the water segregated pockets observed in various aqueous binary mixtures, such as water-alcohol mixtures, for example. In the present study, we demonstrate through classical molecular dynamics studies of the lifetime distributions of the hydrogen bonds in different types of binary mixtures, that these lifetimes exhibit the same universal features in the case of the pure liquids, independently of the species concentrations.

Camel back shaped Kirkwood-Buff integrals.

Some binary mixtures, such as specific alcohol-alkane mixtures or even water-tbutanol, exhibit two humps "camel back" shaped Kirkwood-Buff integrals (KBIs). This is in sharp contrast with the usual KBIs of binary mixtures having a single extremum. This extremum is interpreted as the region of maximum concentration fluctuations, usually occurs in binary mixtures presenting appreciable micro-segregation, and corresponds to where the mixture exhibits a percolation of the two species domains.

Universal features in the lifetime distribution of clusters in hydrogen-bonding liquids.

Hydrogen-bonding liquids, typically water and alcohols, are known to form labile structures (network, chains, ); hence, the lifetime of these structures is an important microscopic parameter, which can be calculated computer simulations. Since these cluster entities are mostly statistical in nature, one would expect that, in the short-timescale regime, their lifetime distribution would be a broad Gaussian-like function of time, with a single maximum representing their mean lifetime, and be weakly dependent on criteria such as the bonding distance and angle, much similar to non-hydrogen-bonding simple liquids, while the long-timescale regime is known to have some power law dependence. Unexpectedly, all the hydrogen-bonding liquids studied herein, namely water and alcohols, display three highly hierarchical specific lifetimes, in the sub-picosecond range 0-0.

Comparative analysis of ethanol dynamics in aqueous and non-aqueous solutions.

In this study, we compare the results for vibrational, reorientational and hydrogen bond dynamics of ethanol in water and in hexane across the whole concentration range. Water and hexane are both commonly used as solvents, but so far, it has been unclear to what extent they modify the solute dynamics. Ethanol is chosen as the solute because it is an aliphatic molecule that is miscibile with both solvents.

Thermodynamic, structural and dynamic properties of selected non-associative neat liquids.

Non-associative neat liquids benzene, acetone and carbon tetrachloride have been examined via molecular dynamics simulations. Several models of each neat liquid have been simulated, and selected thermodynamic and structural results are presented. However, the models have been compared mainly in terms of their dynamic quantities.

The microscopic structure of cold aqueous methanol mixtures.

The evolution of the micro-segregated structure of aqueous methanol mixtures, in the temperature range 300 K-120 K, is studied with computer simulations, from the static structural point of view. The structural heterogeneity of water is reinforced at lower temperatures, as witnessed by a pre-peak in the oxygen-oxygen structure factor. Water tends to form predominantly chain-like clusters at lower temperatures and smaller concentrations.

Micro-heterogeneity versus clustering in binary mixtures of ethanol with water or alkanes.

Ethanol is a hydrogen bonding liquid. When mixed in small concentrations with water or alkanes, it forms aggregate structures reminiscent of, respectively, the direct and inverse micellar aggregates found in emulsions, albeit at much smaller sizes. At higher concentrations, micro-heterogeneous mixing with segregated domains is found.