Heats of Formation of Medium-Sized Organic Compounds from Contemporary Electronic Structure Methods

Computational electronic structure calculations are routinely undertaken to predict thermodynamic properties of various species. However, the application of highly accurate wave function theory methods, such as the gold standard coupled cluster approach including single, double, and partly triple,excitations in perturbative fashion; CCSD(T), to large molecules is limited due to.high computational cost. In this work) the promising domain based local pair natural orbital coupled cluster approach, DLPNO-CCSD(T), has been,tested to reproduce 113 accurate formation enthalpies of Medium-sized molecules (few dozens heavy atoms) important for bio- and combustion cherrlistry via the reaction based Feller-Peterson-Dixoft approach. For comparisop,, eight density functional theory (B3LYP, B3LYP-D3) PBEO, PBEO-D3, M06, M06-2X, omega B97X-D3, and omega B97M-V) and MP2-based (B2PLYP-b3, PWPB95-D3, B2T-PLYP, B2T-PLYP-D, B2GP-PLYP, DSDPBEP86-D3, SCS-MP2, and 00-:SCS-MP2) methods have been tested, The worst performance, has been obtained for the standard hybrid DFT functionals, PBEO (mean unsigned-error (MUE)/thean signed error (ABE) = 9.1/6.0 kcal/mol) and B3LYP (MUE/MSE = 13.5/-13.3 kcal/mol). The influence of an empirical dispersion correction term on these functionals' performance is not homogeneous: B3LYP performance is improved (B3LYP-b3 (MUE/MSE-; 6.0/0.8 kcal/mol)); meanwhile PBEO performance is worse (PBEO-D3 (MUE/MSE = 14.1/13.6 kcal/mol));The Minnesota functionals, M06 (N1UE/MSE = 3.8/-2.0 kcal/mol) and M06-2X (MUE/MSE = 3.5/3.0 kcal/mol), and recently developed omega B97X-D3 (MUE/MSE = 3.2/0.2 kcal/mot), and omega B97M-V (ML/E/MSE = 2.2/1.3 kcal/mol) methods provided significantly better formation enthalpies. Enthalpies of similar quality can also be 'obtained from some double hybrid methods (B2PLYR,D3 (MUE/MSE = 4.7/2.0 kcal/ mol), PWPB95-D3 (MUE/MSE = 4.3/3.2 kcal/mol), B2T-PLYP (MUE/MSE, = 4.1/-3.01cal/mol), and B2T-PLYP-D (MUE/ MSE = 3.3/1.7 kcal/mol)). The two spin component staled (SCS) MP2 methods resulted in even smaller errors (SCS-MP2 (MUE/MSB-= 1.9/1.2 kcal/mol) and OO-SCS-MP2 (MUE/MSB = 1.6/0.1-kcal/mol)). The best performance was found for the froaen core (FC):DLPNO-CCSD(T) method with a MUE/MSE of 1.6/+-1,2 kcal/mol. The performance of the DLPNO-CCSD(T) method can be further improved by running the post-SCF calculations on the B3LYP orbitals: the MUE/MSE for the DLPNO-CCSD(T,B3LYP) approximation is 1.2/-0.4 kcal/mol. We recommend the DLPNO-CCSD(T,B3LYP) method for black box applications in thermodynamics of medium-sized organic molecules when the canonical CCSD(T) calculations with basis sets of reasonable quality are prohibitively expensive.