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>