Predicting Elemental Boiling Points from First Principles

<div>The normal boiling point (NBP) is a fundamental property of liquids and marks the intersection of the Gibbs energies of the liquid and the gas phase at ambient pressure.</div><div>This work provides the first comprehensive demonstration of the calculation of boiling points of atomic liquids through first-principles molecular-dynamics simulations.</div><div>To this end, thermodynamic integration (TDI) and perturbation theory (TPT) are combined with a density-functional theory (DFT) Hamiltonian, which provides absolute Gibbs energies, internal energies, and entropies of atomic liquids with an accuracy of a few meV/atom. </div><div>Linear extrapolation to the intersection with the Gibbs energy of a non-interacting gas phase eventually pins-down the NBPs. While these direct results can already be quite accurate, they are susceptible to a systematic over- or underbinding of the employed density functional. We show how the resulting errors can be strongly reduced by increasing the robustness of the method through a simple linear correction based on a high-level theoretical or experimental cohesive energy termed $\lambda$-scaling.</div><div>By carefully tuning the technical parameters, the walltime per element could be reduced from weeks to about a day (10-20k core-hours), which enabled extensive testing for B, Al, Na, K, Ca, Sr, Ba, Mn, Cu, Xe and Hg. </div><div>This comprehensive benchmark demonstrates the excellent performance and robustness of the approach with a mean absolute deviation (MAD) of less than 2% from experimental NBPs and very similar accuracy for liquid entropies (MAD 2.3 J/(mol*K), 2% relative). In some cases, the uncertainty in the predictions are several times smaller than the variation between literature values, allowing us to clear out ambiguities in the NBPs of B and Ba.</div>

Predicting Elemental Boiling Points from First Principles

<div>The normal boiling point (NBP) is a fundamental property of liquids and marks the intersection of the Gibbs energies of the liquid and the gas phase at ambient pressure.</div><div>This work provides the first comprehensive demonstration of the calculation of boiling points of atomic liquids through first-principles molecular-dynamics simulations.</div><div>To this end, thermodynamic integration (TDI) and perturbation theory (TPT) are combined with a density-functional theory (DFT) Hamiltonian, which provides absolute Gibbs energies, internal energies, and entropies of atomic liquids with an accuracy of a few meV/atom. </div><div>Linear extrapolation to the intersection with the Gibbs energy of a non-interacting gas phase eventually pins-down the NBPs. While these direct results can already be quite accurate, they are susceptible to a systematic over- or underbinding of the employed density functional. We show how the resulting errors can be strongly reduced by increasing the robustness of the method through a simple linear correction based on a high-level theoretical or experimental cohesive energy termed $\lambda$-scaling.</div><div>By carefully tuning the technical parameters, the walltime per element could be reduced from weeks to about a day (10-20k core-hours), which enabled extensive testing for B, Al, Na, K, Ca, Sr, Ba, Mn, Cu, Xe and Hg. </div><div>This comprehensive benchmark demonstrates the excellent performance and robustness of the approach with a mean absolute deviation (MAD) of less than 2% from experimental NBPs and very similar accuracy for liquid entropies (MAD 2.3 J/(mol*K), 2% relative). In some cases, the uncertainty in the predictions are several times smaller than the variation between literature values, allowing us to clear out ambiguities in the NBPs of B and Ba.</div>

Accurate elemental boiling points from first principles

Thermodynamic integration with a DFT Hamiltonian has been used to obtain accurate absolute Gibbs energies of atomic liquids and normal boiling points in excellent agreement with experimental references (MAD < 2%).