Isomers of 1-nitroso-3-nitro-1,2,4-triazol-5-one-2-oxide are of interest in the contest of high explosives and were found to have true local energy minima at the hybrid DFT-B3LYP/aug-cc-pVDZ level. The optimised structures, vibrational frequencies and thermodynamic values for triazol-5-one-N-oxides have been obtained in the ground state. Kamlet-Jacob equations were used to evaluate the performance of model compounds based on the predicted density and the calculated heat of explosion. The detonation properties (D=10.15-10.46km/s, P=50.86-54.25GPa) of designed compounds were found to be promising compared with 1,3,5-trinitro-1,3,5-triazine (D=8.75km/s, P=34.7GPa), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (D=8.96km/s, P=35.96GPa), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (D=9.20km/s, P=42.0GPa) and octanitrocubane (D=9.90km/s, P=48.45GPa). The replacement of secondary hydrogen by nitroso group appears to be a particularly promising area for investigation since it may lead to the desirable consequences of higher heat of explosion, higher density and thus detonation performance.