Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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HF vs MP2 Bad vib. Calc. vs exp. Big anharmonicity Electrostatics Charges Mulliken CHELP Aim ESP Dipole Dipole Dipole angle Dipole calculation types Quadrupole Polarizability Spin Spin density Entropy and Heat Capacity Entropy Reaction entropy Heat Capacity Reaction Reaction Energy 0K Reaction Energy 298K Isodesmic reactions Transition State Transition state Transition state frequencies Transition state geometries IRC Lookup by property By frequency Comparisons Geometry Bonds, angles Bond, angle, or dihedral DFT grid size on point group DFT grid on bond length Core correlation - bond length Same bond/angle many molecules Isoelectronic diatomics Isoelectronic triatomic angles Average bond lengths Rotation Rotational Constants Products of moments of inertia Point group Vibrations Vibrations 2 calculations Frequency differences One frequency Zero point energy Intensity Intensity for one mode Vibrational intensities Reduced mass comparison Anharmonic Triatomic Scale factors Energy Reaction Reaction Energy 0K Reaction Energy 298K Atomization 0K Atomization 298K Single point vs optimized DFT grid size on energy Semiempirical enthalpy Internal rotation Similar molecules Conformation Sets of isomers Sets of tautomers Isomers Entropy Entropy Heat capacity Entropy of several molecules Integrated heat capacity Reaction entropy Electrostatics Dipole Polarizability Several molecules Quadrupole Ion Compare Ionzation energy Koopman ionization energy Koopman IE for a few molecules Compare Electron affinity Compare Proton affinity Protonation Site Resources Info on Results Calculations Done Method and basis set List molecules One molecule Multiple conformers, states Multiple conformers, states Basis functions used I/O files Input/output files MOL file Z-matrix wfn files Glossary Conversion Forms B to I, I to B Angle formulas Integrated heat Capacity Calculating Enthalpy Links NIST Links NIST webbook bibliographic data CCCBDB Experimental data External links Basis Set Exchange Computational Chemistry List Thermochemistry in Gaussian Minnesota Database Collection Benchmark Energy and Geometry Point Groups Thermochemistry Thermochemistry Molecules with good enthalpy A → B + C Reference states Tutorials Vibrations Why scale vibrations Zero-point energies Entropy Methyl rotor entropy Entropy and conformations Energy Getting enthalpy of formation Vertical vs adiabatic IE Thermo from calculations Electrostatics Dipole parts by point group Quadrupoles Geometry Angle formulas Cost Cost Comparison Timings Comparison Bad Calculations Geometry Bad moment of inertia Bad Calculated Bond Lengths Bad point group Worst molecules Vibrations Bad vib. Calc. vs exp. Bad Vib. HF vs MP2 Bad scale factors Low excited states Oddities NaCN Is not linear FAQ Help Units Choose Units Energy Bond length Rotational Constant Moment of Inertia Dipole and Quadrupole Polarizability Explanations Hartree cm-1 Debye Credits Just show me Show me a calculated geometry Summary Using older interface Limit Basis sets Method options List Recent molecules Choose a few Molecules Number of atoms By heavy atoms Diatomics InChI Deuterated Dimers Geometry Point group Point group count Bonds types Isodesmic reactions Bad point group Multiple conformers, states Vibrations Big anharmonicity Energy Enthalpy at 0 Kelvin Similar molecules Similar Isomers Cis/trans Tautomers Multiple conformers, states Ions, Dipoles, etc. List Ions Ionization changes point group Dipole Quadrupole Polarizability Proton Affinities Index of CCCBDB Feedback Error form Wants
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Listing of experimental geometry data for HNCNH (diiminomethane)

Rotational Constants (cm^-1)

Point Group C₂

Internal coordinates

Bond descriptions