Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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All data (experiment and calculated) in the CCCBDB for C₅H₄N₄ (purine)

Property		Experiment	Calculated	Comparison
Energies Entropies	Enthalpy 298.15K
	Enthalpy 0K
	Energy 0K		256
	Energy 298.15K		249
	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)		0
	Nuclear Repulsion Energy		253
	HOMO-LUMO Energies		256
	Barriers to Internal Rotation		0
Geometries	Cartesians		256
	Internal Coordinates		255
	Products of moments of inertia		243
	Rotational Constants		250
	Point Group		257
Vibrations	Vibrational Frequencies		247
	Vibrational Intensities		251
	Zero-point energies		247
	Vibrational scaling factors
	Anharmonic frequencies and constants
	Raman frequencies and intensities		0
Electronic States	Electronic states	x	0
Electrostatics	Atom charges		176
	Dipole		180
	Quadrupole		176
	Polarizability		207
Other results	Spin		0
	Number of basis functions		25
	Conformations		1