Cross Second Virial Coefficients of the H₂O-H₂ and H₂S-H₂ Systems from First-Principles

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• Accurate intermolecular potentials are crucial for understanding gas properties.
• Previous theoretical studies exist for water-hydrogen interactions.
• Experimental or theoretical data for hydrogen sulfide-hydrogen interactions are lacking.

Purpose of the Study:

• To compute cross second virial coefficients (B12) for water-hydrogen and hydrogen sulfide-hydrogen systems.
• To develop new intermolecular potential energy surfaces (PESs) for these interactions.
• To provide the first theoretical predictions for B12 in the hydrogen sulfide-hydrogen system.

Main Methods:

• High-level quantum-chemical ab initio calculations up to CCSDT(Q).
• Correction for scalar relativistic effects.
• Mayer-sampling Monte Carlo approach to extract B12 from PESs.

Main Results:

• New PESs were generated for water-hydrogen and hydrogen sulfide-hydrogen pairs.
• Calculated B12 values for water-hydrogen validate existing theoretical data.
• First-principles B12 values for hydrogen sulfide-hydrogen were obtained across a wide temperature range (150-2000 K).

Conclusions:

• The study provides reliable B12 coefficients for industrially relevant gas mixtures.
• The developed PESs and B12 data serve as a benchmark for future studies.
• This work fills a critical data gap for the hydrogen sulfide-hydrogen system.