National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

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Compare heats of formation at 298K for semiempirical levels and group additivity methods

Group additivity method as implemented in the NIST Chemistry webbook (

Enter Formula

or choose by chemical groups.

Rules for chemical formula

Species in the CCCBDB

Going to the group selection page allows the selection of molecules with certain chemical groups, such as C=O bonds or NH2 groups. A list of species that match the group criteria is returned and one or more may be selected.