Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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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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All data (experiment and calculated) in the CCCBDB for C₄H₄ (cyclobutadiene)

Property		Experiment	Calculated	Comparison
Energies Entropies	Enthalpy 298.15K
	Enthalpy 0K
	Energy 0K		394
	Energy 298.15K		338
	Atomization Enthalpy 298.15K		0
	Atomization Enthalpy 0K		0
	Entropy (298.15K)		0
	Entropy at any temperature		0
	Integrated Heat Capacity		0
	Heat Capacity (Cp)	x	0	x
	Nuclear Repulsion Energy		391
	HOMO-LUMO Energies		391
	Barriers to Internal Rotation		0
Geometries	Cartesians		391
	Internal Coordinates		389
	Products of moments of inertia		374
	Rotational Constants		386
	Point Group		399
Vibrations	Vibrational Frequencies	fun.	376	x
	Vibrational Intensities		368
	Zero-point energies		376
	Vibrational scaling factors
	Anharmonic frequencies and constants
	Raman frequencies and intensities		8
Electronic States	Electronic states	x	0
Electrostatics	Atom charges		244
	Dipole		315
	Quadrupole		281
	Polarizability		249
Other results	Spin		0
	Number of basis functions		6
	Conformations		2	x