National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 19April 2018
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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All results from a given calculation for HNO2 (Nitrous acid)

using model chemistry: MP4/3-21G

States and conformations

State Conformation minimum conformation conformer description state description
1 1 yes CS 1A'
Energy calculated at MP4/3-21G
Energy at 0K-203.872200
Energy at 298.15K-203.867836
HF Energy-203.449362
Nuclear repulsion energy64.797992
The energy at 298.15K was derived from the energy at 0K and an integrated heat capacity that used the calculated vibrational frequencies.
Vibrational Frequencies calculated at MP4/3-21G
Mode Number Symmetry Frequency (cm-1) Scaled Frequency (cm-1) IR Intensities (km mol-1)
1 A' 3371 3269  
2 A' 1295 1256  
3 A' 1077 1044  
4 A' 773 750  
5 A' 504 489  
6 A" 527 511  

Unscaled Zero Point Vibrational Energy (zpe) 3773.0 cm-1
Scaled (by 0.9698) Zero Point Vibrational Energy (zpe) 3659.1 cm-1
See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.
Rotational Constants (cm-1) from geometry optimized at MP4/3-21G
2.63054 0.36378 0.31959

See section I.F.4 to change rotational constant units
Geometric Data calculated at MP4/3-21G

Point Group is Cs

Cartesians (Å)
Atom x (Å) y (Å) z (Å)
H1 -1.842 -0.162 0.000
O2 -0.964 -0.649 0.000
N3 0.000 0.568 0.000
O4 1.194 0.173 0.000

Atom - Atom Distances (Å)

  H1 O2 N3 O4

picture of Nitrous acid
More geometry information

Calculated Bond Angles

atom1 atom2 atom3 angle atom1 atom2 atom3 angle
H1 O2 N3 99.411 O2 N3 O4 110.073
Electronic energy levels

Electronic state

Charges, Dipole, Quadrupole and Polarizability