Earlier [1, 2], we developed a protocol for prediction of the gas-phase enthalpies of formation of the CHON-containing closed-shell compounds with the expanded uncertainty of (2.5 to 3) kJ mol–1. The protocol combines the total energies of molecules from local CCSD(T)/aug-cc-pVQZ//DF-MP2/aug-cc-pVQZ, B3LYP-D3BJ/def2-TZVP frequencies, and the effective enthalpies of formation of atoms derived using the critically evaluated experimental enthalpies of formation. The accuracy of experimental data confirmed by multiple measurements was found essential for the success of the method. In this work, we extend this protocol to the sulfur-containing compounds. The major challenge encountered from the beginning was that, for most compounds, only a single experimental enthalpy of formation is available (i.e., no multiple independent confirmations), and the procedure for selection of the training set established to the previous work [1] needs to be revised. Furthermore, the available experimental data for compounds with specific functional groups of interest typically come from the same laboratory and may potentially be biased while being consistent across homologous series. Consequently, a compromise training set of sulfur-containing compounds was assembled based on diversity in both the functional groups present and the origins of the data. The initial results identify several atomic types for sulfur whose post-CCSD(T) contributions differ by more than 15 kJ mol–1, a much greater difference as compared to that observed for carbon types [2]. The expanded uncertainty of the proposed protocol for sulfur-containing compounds is close to 3 kJ mol–1. The performance of the protocol was also tested against the experimental enthalpies of formation published recently.

Efficient estimation of formation enthalpies with local coupled-cluster methods: Extension to sulfur

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.