Bad CalculationsThe following links illustrate calculations that produce poor results for certain model chemistries and molecules.
A. Bad geometries
- Bad calculated geometries by comparing products of moments of inertia.
- Bad calculated bond lengths
- List molecules whose point groups differ from experiment
- Bad calculated bond lengths sorted by molecule
B. Bad vibrational frequencies
- Vibrational frequencies whose frequencies increase from HF/6-31G* to MP2/6-31G*, which may indicate a problematic molecule or a problematic vibrational mode.
- Bad predicted vibrational frequencies based on differences and ratios with experimental frequencies
- Questionable results by comparing vibrational scaling factors
C. Low lying excited state
- Molecules with negative natural orbital occupation numbers. A warning that the ground state may be multiconfigurational.