The fully optimized geometries and electronic structures of seven nitramino derivatives of tetrazole are calculated by ab initio method at HF/6-31G^* level. The results show that the tetrazole ring is approximately planar. The aromaticity for neutral 2H-tetrazoles is higher than that for the corresponding 1H-isomers. The nitramino group in 5-nitramino-1H-tetrazole is co-planar to the ring due to the hydrogen bonding between O(10) and H(11), whereas in others the nitramino groups are perpendicular to the ring planes. The calculated energy results at different theoretical levels show that electron correlation effects in the title compounds are greater. The total energies of the neutral 1H-tetrazoles are higher than those of the 2H- isomers. Among three anions 5-nitraminotetrazole anion is the most stable. The protonation sites and coordination modes of the title compounds are elucidated based on the charge distribution. The IR spectra, thermodynamic properties, i, e. standard molar enthalpy, standard molar heat capacity and standard molar entropy of the title compounds are calculated. Finally, temperature-dependent functions for heat capacities in the form (a+bT+cT^2) in the 300K～1000K range are obtained. Comparison shows that the title compounds have similar thermodynamic properties and as the temperature rises, the difference between the thermodynamic functions of the neutral species and the corresponding anions increases.

Key words: AB INITIO CALCULATION, TETRAZOLE P, ELECTRONIC STRUCTURE, GEOMETRICAL ISOMERISM, INFRARED SPECTROPHOTOMETRY, THERMODYNAMIC PROPERTIES, TOTAL ENERGY