The liquidus curve of aqueous methanol mixtures. The high-alcohol concentration region at standard pressure

Abstract

This work extends our previous simulation study on the water/methanol liquidus curve at low methanol concentrations [M. Martínez-Jiménez and A. L. Benavides, J. Chem. Phys. 157, 104502 (2022)]. We now explored methanol-rich mixtures that are located beyond the eutectic point, at p = 0.1 MPa. To our knowledge, the liquidus temperatures for these mixtures have not been obtained before with any simulation technique. In this case, the liquidus temperature curve characterizes the boundary between the liquid methanol/water mixture and a coexistence of a liquid mixture with the β-methanol solid. Direct-coexistence simulations were performed using the combination of the TIP4P/Ice model for water and the OPLS/2016 model for methanol. The obtained liquidus temperatures follow the experimental data trend, although a systematic overestimation is observed. Knowing that this deviation is possibly due to the OPLS/2016 model, which overestimates the methanol melting point, we hope that the information presented in this work will help refine this model, thereby improving the force field for mixtures. In addition, we present the methanol freezing-point depression by water that could be another target property to consider in the design of better models.