Cross Second Virial Coefficient of the H2O–CO System from a New Ab Initio Pair Potential

Abstract

AbstractThe cross second virial coefficient $$B_{12}$$ B 12 for the interaction between water (H2O) and carbon monoxide (CO) was obtained with low uncertainty at temperatures from 200 K to 2000 K employing a new intermolecular potential energy surface (PES) for the H2O–CO system. This PES was fitted to interaction energies determined for about 58 000 H2O–CO configurations using high-level quantum-chemical ab initio methods up to coupled cluster with single, double, and perturbative triple excitations [CCSD(T)]. The cross second virial coefficient $$B_{12}$$ B 12 was extracted from the PES using a semiclassical approach. An accurate correlation of the calculated $$B_{12}$$ B 12 values was used to determine the dilute gas cross isothermal Joule–Thomson coefficient, $$\phi _{12}=B_{12}-T(\mathrm {d}B_{12}/\mathrm {d}T)$$ ϕ 12 = B 12 - T ( d B 12 / d T ) . The predicted values for both $$B_{12}$$ B 12 and $$\phi _{12}$$ ϕ 12 agree reasonably well with the few existing experimental data and older calculated values and should be the most accurate estimates of these quantities to date.