National Institute of Standards and Technology

Computational Chemistry Comparison and Benchmark DataBase
Release 22	May 2022
NIST Standard Reference Database 101

I	Introduction
II	Experimental data
III	Calculated data
IV	Data comparisons
V	Cost comparisons
VI	Input and output files
VII	Tutorials and Units
VIII	Links to other sites
IX	Feedback
X	Older CCCBDB versions
XII	Geometries
XIII	Vibrations
XIV	Reaction data
XV	Entropy data
XVI	Bibliographic data
XVII	Ion data
XVIII	Bad calculations
XIX	Index of properties
XX	H-bond dimers
XXI	Oddities

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The National Institute of Standards and Technology (NIST) is an agency of the U.S. Department of Commerce.

Please send questions, comments, corrections, additions and suggestions to cccbdb@nist.gov.

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.