National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

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II.A.1. (XV.A.)

Listing of experimental data for I2 (Iodine diatomic)

State Conformation
1Σg D*H
Enthalpy of formation (Hfg), Entropy, Integrated heat capacity (0 K to 298.15 K) (HH), Heat Capacity (Cp)
Property Value Uncertainty units Reference Comment
Hfg(298.15K) enthalpy of formation 62.42 0.08 kJ mol-1 Gurvich
Hfg(0K) enthalpy of formation 65.50 0.08 kJ mol-1 Gurvich
Entropy (298.15K) entropy 260.68   J K-1 mol-1 Gurvich
Integrated Heat Capacity (0 to 298.15K) integrated heat capacity 10.12   kJ mol-1 Gurvich
Heat Capacity (298.15K) heat capacity 36.89   J K-1 mol-1 Gurvich
Information can also be found for this species in the NIST Chemistry Webbook
Vibrational levels (cm-1) vibrations
Mode Number Symmetry Frequency (cm-1) Frequency Reference Intensity (km mol-1) Int. unc. Intensity Reference Comment
1 Σ 215        

vibrational zero-point energy: 107.3 cm-1
Calculated vibrational frequencies for I2 (Iodine diatomic).
Rotational Constants (cm-1) rotational constants
See section I.F.4 to change rotational constant units
A B C reference comment
  0.03737 0.03737 webbook Be

Calculated rotational constants for I2 (Iodine diatomic).

Product of moments of inertia moments of inertia
451.1006amu Å2   7.490819E-38gm cm2
Geometric Data
picture of Iodine diatomic

Point Group

Internal coordinates
distances (r) in Å, angles (a) in degrees, dihedrals (d) in degrees

Description Value unc. Connectivity Reference Comment
Atom 1 Atom 2 Atom 3 Atom 4
rII 2.665   1 2 Gurvich re


Atom x (Å) y (Å) z (Å)
I1 0.0000 0.0000 0.0000
I2 0.0000 0.0000 2.6655

Atom - Atom Distances bond lengths
Distances in Å

  I1 I2
I1   2.6655
I2 2.6655  

Calculated geometries for I2 (Iodine diatomic).

Bond descriptions

Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
I-I 1


Atom 1 Atom 2
I1 I2
Electronic energy levels (cm-1)
Energy (cm-1) Degeneracy reference description
0 1   1Σg

Ionization Energies (eV)

Ionization Energy I.E. unc. vertical I.E. v.I.E. unc. reference
9.307 0.000 9.356   webbook
Dipole, Quadrupole and Polarizability
Electric dipole moment dipole
For a molecule with D∞h symmetry there is no dipole.
Electric quadrupole moment quadrupole
Calculated electric quadrupole moments for I2 (Iodine diatomic).

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squib reference DOI
Gurvich Gurvich, L.V.; Veyts, I. V.; Alcock, C. B., Thermodynamic Properties of Individual Substances, Fouth Edition, Hemisphere Pub. Co., New York, 1989 10.1351/pac198961061027
webbook NIST Chemistry Webbook (  

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