Predicting vapor liquid equilibria using density functional theory: A case study of argon

Area of Science:

• Computational Chemistry
• Chemical Physics

Background:

• Predicting vapor-liquid equilibria (VLE) for systems with weak van der Waals (vdW) interactions is computationally demanding.
• Traditional Kohn-Sham density functional theory (DFT) struggles with accurately describing vdW forces due to limitations in capturing long-range correlations.
• Advanced DFT methods, including dispersion corrections and nonlocal functionals, aim to improve vdW interaction modeling with varying success.

Purpose of the Study:

• To evaluate the performance of various DFT functionals and second-order Møller-Plesset perturbation theory (MP2) for predicting the VLE of argon.
• To assess the accuracy of different computational methods in determining critical and structural properties relevant to VLE.

Main Methods:

• First principles Monte Carlo simulations were employed to predict VLE properties.
• Several dispersion-corrected DFT functionals (PBE-D3, BLYP-D3, rVV10) were used to compute vapor-liquid coexistence curves.
• MP2 theory and other DFT functionals (PBE0-D3, M06-2X-D3) were utilized to calculate liquid density at a specific state point.

Main Results:

• The PBE-D3 functional demonstrated superior performance in predicting the VLE of argon compared to BLYP-D3 and rVV10.
• MP2 theory accurately reproduced the density and structural characteristics of argon's first solvation shell at 85 K and 1 bar.
• The study provides a comparative analysis of different computational approaches for VLE prediction.

Conclusions:

• Dispersion-corrected DFT, particularly PBE-D3, offers a promising avenue for accurate VLE predictions of systems dominated by vdW interactions.
• MP2 theory is reliable for capturing liquid-phase structural details and density, complementing DFT predictions.
• This work contributes to advancing first principles methods for understanding and predicting phase equilibria in molecular systems.