Accurate ab initio computation of thermochemical data for C3Hx species

Uncertainty quantification in thermochemistry, benchmarking electronic structure computations, and Active Thermochemical Tables

“…Unprecedented accuracy and reliability makes ATcT values very attractive for tweaking and benchmarking state‐of‐the‐art electronic structure methods, such as HEAT, W4, and others . In addition, ATcT have introduced a number of useful features that were never before available in thermochemistry, such as painless updates with new knowledge, or the availability of full covariance matrix, which allows a detailed analysis of the distributed provenance of each value, identification of additional determinations that would efficiently boost the knowledge content of the TN and so forth.…”

Active Thermochemical Tables: dissociation energies of several homonuclear first-row diatomics and related thermochemical values

“…6 In contrast to this, Huber and Herzberg [31] termed the determination of Messerle and Krauss [30] as 'somewhat doubtful' and listed D 0 (C 2 ) = 599 kJ/mol (with an implied uncertainty of about ±9 kJ/mol) based on high-temperature measurements of Brewer et al [32] and of Kordis and Gingerich [33]. Gurvich et al [12,13] examined nearly all high-temperature measurements that were available at the time [33][34][35][36][37][38][39][40], and ultimately anchored the thermochemistry of C 2 on the same spectroscopic measurement as JANAF, but reinterpreted it as implying D 0 (C 2 ) = 600 ± 10 kJ/ mol.…”

“…In spite of the fact that the presence of C 2 is clearly visible in nearly every hydrocarbon flame (quoting Hoffmann [41]: 'the lovely blue color of hot hydrocarbon flames is due in large part to emission from excited C 2 molecules on their way to soot or CO 2 '), and in spite of numerous detailed spectroscopic studies of this molecule [42][43][44][45][46][47][48][49][50][51], there is very little in terms of accurate experimental determinations that could help define D 0 (C 2 ). Among the top fifty provenance contributors to the ATcT value, only four are experimental 6 Note that there is an inconsistency in the JANAF Tables [14,15]: the listed enthalpy of formation of C 2 was derived in the third edition [14] by combining the assumed bond dissociation energy of 589.7 ± 3.8 kJ/mol with an older value for the enthalpy of formation of C atom, which is lower by 1.7 kJ/mol than the listed value. Thus, from the listed enthalpies of formation for C 2 and C, one nominally obtains D 0 (C 2 ) = 593.1 ± 3.9, or 3.4 kJ/mol higher than their original assumption.…”

“…Rather than experiment, the relevant provenance contributors in the current version of ATcT derive from theory: the bond dissociation energy and the energy for loss of two hydrogen atoms from acetylene based on W4. , as well as the C-H bond dissociation energy of C 2 H from an approach that utilized explicitly correlated coupled-cluster methods [6], as well as the same bond energy from a CCSD(T)/CBS-based approach [58]. Although the current ATcT value for D 0 (C 2 ) is dominated by virtual (i.e., computational) determinations, rather than actual (i.e., experimental) determinations, this was not necessarily the case in earlier versions of the ATcT TN.…”

“…These characteristics of the ATcT thermochemical values make them very desirable for developing and benchmarking highly accurate state-of-the-art electronic structure approaches [3][4][5][6].…”