Computational investigations of the thermodynamic properties of size-selected water and Ar–water clusters: high-pressure transitions

Abstract

Classical parallel-tempering Monte Carlo simulations in the isothermal-isobaric ensemble were carried out for the (H2O)20 and Ar(H2O)20 clusters, over a wide range of temperatures (30-1000 K) and pressures (3 kPa-10 GPa) in order to study their thermodynamic properties and structural changes. The TIP4P/ice water model is employed for the water-water interactions, while both semiempirical and ab initio-based potentials are used to model the interaction between the rare-gas atoms and the water molecules. Temperature-pressure phase diagrams for these cluster systems were constructed by employing a two-dimensional multiple-histogram method. Structural changes were detected by analyzing the heat capacity landscape and the Pearson correlation coefficient profile for the interaction energy and volume. Those at high pressure correspond to solid-to-solid transitions and are found to be related to clathrate-like cages around the Ar atom. It is also shown that the formation and thermodynamic stability of such structures are determined by the intermolecular interaction between the rare-gas atoms and the host water molecules.

A Systematic Protocol for Benchmarking Guest–Host Interactions by First‐Principles Computations: Capturing CO2 in Clathrate Hydrates

“…[39] and references therein). Nowadays, most of the molecular dynamics (MD) simulations still rely on empirical or semiempirical force fields as an important tool for investigating processes, such as the nucleation, growth, structural organization, and cage occupancy of clathrate hydrates, as well as the dissolution of the guest gas in water, [40][41][42][43][44][45][46][47][48][49][50] whereas for ab initio simulations, issues such as computational efficiency,s ystem-size scaling, and accurate electronic structuret reatments are of importance,w ith density functional theory (DFT) approaches [36,38,[51][52][53][54][55] being, more recently,a lso valuable in studyings uch inclusion compounds. In this vein, energy benchmarksf rom accurate quantum-mechanical calculations are essential for testing both force fields and DFT methods.…”

Fully Coupled Quantum Treatment of Nanoconfined Systems: A Water Molecule inside a Fullerene C60

“…[1][2][3][4][5] Such nanoconfined systems have been the topic of broad research, focused on their different chemical and physical behavior compared with the bulk systems, as the confined molecules are subject to surrounding host medium, resulting specific unexpected effects on properties and dynamics of the guest moieties. So far, various types of nanocavities have been investigated, such as those of clathrate hydrates, [6][7][8][9][10][11][12][13][14][15] rare gas nanodroplets, [16][17][18][19][20][21] fullerenes, 22 etc.…”

Assessing Intermolecular Interactions in Guest-Free Clathrate Hydrate Systems

“…Up to now, from the theoretical perspective, the investigations are still ongoing towards the development of fundamental physico-chemical processes in clathrate exploitation, including their microscopic structural evolution, aiming to gain a better understanding of stabilities and storage capacities of their cavities. 2,[8][9][10] The rapid increase in computing power has also led to numerous quantum chemistry calculations on guest-host interactions, as well as a plethora of benchmark computations in large water clusters. [11][12][13][14][15][16][17][18][19][20][21] The results of such studies have shown that ab initio electronic structure methods provide independent and accurate means of reaching a good understanding of the nature of hydrates and description of the underlying guest-host potential.…”