National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 18October 2016
NIST Standard Reference Database 101
IIntroduction
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
IXFeedback
XOlder CCCBDB versions
XIIGeometries
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers
XXIOddities

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XVIII.

Bad Calculations

The following links illustrate calculations that produce poor results for certain model chemistries and molecules.

A. Bad geometries

  1. Bad calculated geometries by comparing products of moments of inertia.
  2. Bad calculated bond lengths
  3. List molecules whose point groups differ from experiment
  4. Bad calculated bond lengths sorted by molecule

B. Bad vibrational frequencies

  1. Vibrational frequencies whose frequencies increase from HF/6-31G* to MP2/6-31G*, which may indicate a problematic molecule or a problematic vibrational mode.
  2. Bad predicted vibrational frequencies based on differences and ratios with experimental frequencies
  3. Questionable results by comparing vibrational scaling factors

C. Low lying excited state

  1. Excited electronic states by CIS

D. Diagnostics

  1. Molecules with negative natural orbital occupation numbers. A warning that the ground state may be multiconfigurational.