Gibbs-ensemble Monte Carlo simulations for binary mixtures

<p>We explore the performance of the Gibbs-ensemble Monte Carlo simulation method by calculating the miscibility gap of H<sub>2</sub>-He mixtures with analytical exponential-six potentials [1]. We calculate demixing curves for pressures up to <em>500</em> kbar and temperatures up to <em>1800</em> K. Our results are in good agreement with <em>ab initio </em>simulations in the non-dissociated region of the phase diagram. Next, we determine new parameters for the Stockmayer potential [2] to model the interactions in the H<sub>2</sub>O-H<sub>2</sub>O system for temperatures of <em>1000</em> K < <em>T</em> < <em>2000</em> K. The corresponding miscibility gap of H<sub>2</sub>-H<sub>2</sub>O mixtures was determined and we calculated demixing curves for pressures up to <em>150</em> kbar and temperatures up to <em>2000</em> K. Our results show reasonable agreement with previous experimental data of Bali <em>et al.</em> [3]. These results are important for interior and evolution models for ice giant planets [4].<br><br><strong>References</strong><br>[1] A. Bergermann, M. French, M. Schöttler and R. Redmer, Phys. Rev. E, 103 (2021)<br>[2] W. Stockmayer, The Journal of Chemical Physics 9, S. 398-402 (1941)<br>[3] E. Bali, A. Audétat and H. Keppler, Nature, 495, 7440 (2013)<br>[4] R. Helled, N. Nettelmann and T. Guillot, Space Science Reviews, 216 (2020)<br><br><br><br><br></p>

Gibbs-ensemble Monte Carlo simulation of H2–H2O mixtures

The miscibility gap in H2–H2O mixtures is investigated by conducting Gibbs-ensemble Monte Carlo simulations. Our results indicate that H2–H2O immiscibility regions may have a significant impact on the structure and evolution of ice giant planets.

Ab initio Gibbs ensemble Monte Carlo simulations of the liquid–vapor equilibrium and the critical point of sodium

We extend the application of the ab initio Gibbs ensemble method to the metallic system by including the contribution of excited electronic states.

Phase Behavior of Pure Components - Carbon Dioxide, n-Decane and Argon: Test of Simulation Software-Molecular Simulation Techniques (Gibbs Ensemble Monte Carlo Simulation)

Phase equilibrium of CO 2 decane liquids plays an important role in long-term behavior and storage of carbon dioxide in deep underground reservoirs and oil and gas wells. To this end, the Gibbs ensemble Monte Carlo (GEMC) simulation in the constant volume (canonical NVT ) ensemble were carried out to calculate the phase behavior of pure components viz- carbon dioxide, n-decane and argon. The Transferable Potential for Phase Equilibria (TraPPEUA) force fields was used to predict the vaporliquid equilibria coexistence behavior of decane and argon, while Elementary Physical Model 2 (EPM2 model) for carbon dioxide, were performed with constant volume GEMC simulation. From the results obtained, TraPPE-UA force field successfully studied the phase behavior of n -decane and argon, and by using rescaled EPM2 model the vapour-liquid equlibria of carbon dioxide (CO 2 ) was examined their miscibility (solubility) and the possibility of storing and tracking stored carbon dioxide in a reservoir (geological well).

A Molecular Mechanism for Azeotrope Formation in Ethanol/benzene Binary Mixtures Through Gibbs Ensemble Monte Carlo Simulation

Azeotropes have been studied for decades due to the challenges they impose on separation processes but fundamental understanding at the molecular level remains limited. Although molecular simulation has demonstrated its capability of predicting mixture vapor-liquid equilibrium (VLE) behaviors, including azeotropes, its potential for mechanistic investigation has not been fully exploited. In this study, we use the united atom transferable potentials for phase equilibria (TraPPE-UA) force-field to model the ethanol/benzene mixture, which displays a positive azeotrope. Gibbs ensemble Monte Carlo (GEMC) simulation is performed to predict the VLE phase diagram, including an azeotrope point. The results accurately agree with experimental measurements. We argue that the molecular mechanism of azeotrope formation cannot be fully understood by studying the mixture liquid-state stability at the azeotrope point alone. Rather, azeotrope occurrence is only a reflection of the changing relative volatility between the two components over a much wider composition range. A thermodynamic criterion is thus proposed based on the comparison of partial excess Gibbs energy between the components. In the ethanol/benzene system, molecular energetics shows that with increasing ethanol mole fraction, its volatility initially decreases but later plateaus, while benzene volatility is initially nearly constant and only starts to decrease when its mole fraction is low. Analysis of the mixture liquid structure, including a detailed investigation of ethanol hydrogen-bonding configurations at different composition levels, reveals the underlying molecular mechanism for the changing volatilities responsible for the azeotrope.