Researchers at NIST, the National Institute of Standards and Technology of the United States, have carefully evaluated ORCAs DLPNO-CCSD(T) method. Formation enthalpies for 45 closed-shell compounds composed of C, H, O, and N atoms have been calculated using resolution-of-identity and domain-based local pair-natural orbital coupled cluster, DLPNO–CCSD(T), approximations. The computational results have been compared to thoroughly vetted experimental values.
The researchers found an expanded uncertainty of about 3 kJ·mol–1.
This is competitive with the uncertainty of typical calorimetric measurements.
The researchers conclude: "For the compounds within the stated scope, the methodology is shown to be superior to a representative, more general, and widely used composite quantum chemical method, G4."