Computational Chemistry Comparison and Benchmark DataBase Release 18 (October 2016) Standard Reference Database 101 National Institute of Standards and Technology Home All data for one species Geometry Experimental Calculated Comparisons Bad Calculations Tutorials and Explanations Vibrations Experimental Calculated Scale factors Reactions Entropies Ions List Ions Energy Electron Affinity Proton Affinity Ionization changes point group Experimental One molecule all properties One property a few molecules Geometry Vibrations Energy Electrostatics Reference Data Calculated Energy Optimized Reaction Internal Rotation Orbital Nuclear repulsion energy Correlation Ion Excited State Basis Set Extrapolation Geometry Vibrations Frequencies Zero point energy (ZPE) Scale Factors Bad Calculations Electrostatics Charges Dipole Quadrupole Polarizability Spin Entropy and Heat Capacity Reaction Lookup by property Comparisons Geometry Vibrations Energy Entropy Electrostatics Ion Resources Info on Results Calculations Done Basis functions used I/O files Glossary Conversion Forms Links NIST Links External links Thermochemistry Tutorials Vibrations Entropy Energy Electrostatics Geometry Cost Bad Calculations FAQ Help Units Choose Units Explanations Credits Just show me Summary Using List Recent molecules Molecules Geometry Vibrations Energy Similar molecules Ions, Dipoles, etc. Index of CCCBDB Feedback You are here: Comparisons > Geometry > Bonds, angles > Bond, angle, or dihedral

# Bond lengths, angles, or dihedrals given molecule at different levels of theory

The next several pages ask for
first - a molceule
second - a bond length, angle or dihedral, by choosing 2, 3 or 4 atoms in the molecule

## Select species

Enter formula

The atom numbering does not line up between different methods for some species in the CCCBDB. This can lead to some erroneous geometry comparisons. We are working on correcting this.

Some experimental bond lengths are re values (bottom of well) and some are r0 (vibrational zero point level). The calculations yield re values. For diatomics the experimental values are mostly re. For polyatomics usually r0 is obtained from rotational spectra.

For polyatomics usually only a partial description of the geometry can be derived from the rotational constants, so assumptions are made in determining the geometry, such as all CH bonds in a methyl group have the same length.

#### Rules for chemical formula

• Enter a sequence of element symbols followed by numbers to specify the amounts of desired elements (e.g., C6H6).
• Elements may be in any order.
• If only one of a given atom is desired, you may omit the number after the element symbol.
• Parentheses may be used to group atoms.
• Multiple specifications for an atom will be added. This means that CH3(CH2)4CH3 will be treated the same as C6H14.
• A comma delimited list of several species may be entered.
• Ions are indicated by placing + or - at the end of the formula (CH3+, BF4-, CO3--)

#### Species in the CCCBDB

• Mostly atoms with atomic number less than than 36 (Krypton), except for most of the transition metals. See section I.B.1 for a periodic table view.
• Six or fewer heavy atoms and twenty or fewer total atoms. Exception: Versions 8 and higher have a few substituted benzenes with more than six heavy atoms. Versions 12 and higher have bromine-containing molecules.