All chemicals and solvents were obtained from Aladdin Bio-Chem Technology CO. Ltd (Shanghai, China) and used without further purification. 1,2,4-Oxadiazole-3-carboxyamidoxime (1) was supplied by Xi'an Modern chemistry Research Institute. 13C and 1H NMR spectra were recorded at 298 K on an AV 500 NMR spectrometer (Bruker, Switzerland). Infrared spectra were measured by an EQUINOX 55 Fourier transform infrared spectrometer (Bruker, Germany). Elemental analyses were obtained on the vario EL cube elemental analyzer (Elmentar, Germany). The thermal analysis experiments were recorded on a model TG-DSC STA 499 F3 instrument (NETZSCH, Germany) with dynamic nitrogen atmosphere at a heating rate of 10°C min−1. Single crystal X-ray experiment was carried out on a Bruker Apex II CCD diffractometer equipped with graphite monochromatized Mo Kα radiation (λ = 0.71073 Å) using ω and φ scan mode. Structures were solved by the direct method using SHELXTL and refined by means of full-matrix least-squares procedures on F2 with the programs SHELXL-97. Detonation velocity and detonation pressure data were calculated by program package EXPLO5 (version 6.02). The sensitivity data were determined according to BAM standards by BAM drophammer and BAM friction tester (NATO, 1999 , 2002 ).
CCDC number of compound4 • H2O and compound 6 is 1958390 and 1958391, respectively.
CCDC number of compound