The crystal structure and morphology of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) p-xylene solvate: a joint experimental and simulation study

• Published in: Molecules (Basel, Switzerland) Vol. 19; no. 11; pp. 18574 - 18589
• Main Authors: Shen, Fanfan, Lv, Penghao, Sun, Chenghui, Zhang, Rubo, Pang, Siping
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 13.11.2014; MDPI
• Subjects: Attachment; Aza Compounds - chemistry; CL-20; crystal morphology; Crystal structure; Crystallography, X-Ray; Crystals; Energy; Energy of solution; Explosives; Fourier transforms; Growth models; Heterocyclic Compounds - chemistry; Infrared spectroscopy; Mathematical models; Models, Molecular; molecular dynamic simulation; Morphology; p-xylene; Simulation; solvent effect; Solvents; Spectroscopy, Fourier Transform Infrared; Xylenes - chemistry; Beijing China; China
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules191118574

The crystal structure of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaiso-wurtzitane (CL-20) p-xylene solvate, and the solvent effects on the crystal faces of CL-20 were studied through a combined experimental and theoretical method. The properties were analyzed by thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).The growth morphology of CL-20p-xylene solvate crystal was predicted with a modified attachment energy model. The crystal structure of CL-20p-xylene solvate belonged to the Pbca space group with the unit cell parameters, a=8.0704(12) Å, b=13.4095(20) Å, c=33.0817(49) Å, and Z=4, which indicated that the p-xylene solvent molecules could enter the crystal lattice of CL-20 and thus the CL-20 p-xylene solvate is formed. According to the solvent-effected attachment energy calculations, (002) and (11-1) faces should not be visible at all, while the percentage area of the (011) face could be increased from 7.81% in vacuum to 12.51% in p-xylene solution. The predicted results from the modified attachment energy model agreed very well with the observed morphology of crystals grown from p-xylene solution.