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A new occupancy model for predicting the crystal morphologies influenced by solvent and temperature is proposed. In the model, the attachment energy is corrected by a relative occupancy, which is the occupancy of a solute molecule relative to the total ones of a solute molecule and a solvent molecule. The occupancy is defined proportional to the averaged interaction energy between a solute or solvent molecule and a crystal surface. The validity of the model is confirmed by its successful applications to predict the crystal morphologies of a class of well-known nitroamino explosives hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tertranitro-1,3,5,7tetrazocine and 2,4,6,8,10,12-hexanitrohexaaz-aisowurtzitane grown in solution. Furthermore, the applications of this model regarding concentration, molecular diffusion ability in solution, and mixed solvents are prospected.

is the most powerful explosive applied, and CL-20-based energetic-energetic co-crystals are promising new alternative explosives with tunable power and safety, resulting in much interest in them. This work discusses the structural, electronic and energetic features of three CL-20 polymorphs, β, γ and ε forms, and three CL-20-based energeticenergetic co-crystals, CL-20/TNT, CL-20/HMX and CL-20/BTF. As a result, we find that, relative to the pure CL-20 polymorphs, the co-crystallization of CL-20 with HMX, TNT and BTF cause little molecular deformation except from some torsion of its nitro groups, and the narrower band gaps. And dominantly, the O⋯O, O⋯H and O⋯N interactions hold all the crystal packing. There is possibly thermodynamic and kinetic dominance in the CL-20/TNT and CL-20/HMX, and CL-20/BTF co-crystallization, respectively, in terms of their formation energy. Further, a rough criterion for predicting energetic co-crystal formation is obtained, as the solubility parameter difference of two coformers of a binary energetic co-crystal is less than 8 MPa 0.5 .

This paper presents an investigation on the anisotropic modulus of energetic crystals of b-HMX by using a Hysitron Triboindenter fitted with a Berkovich tip. High quality single crystals of b-HMX, whose densities were determined by high precision density gradient tube (DGT), were used in order to extract the moduli of two orthogonal crystal faces: (010), the maximum growth habit face (termed face 1), and the face which is perpendicular to it (termed face 2). Contrary to common expectation, the moduli of face 1 and face 2 were found to be 23.4 and 26.1 GPa, respectively, indicating a negligible crystal anisotropy of the system. Nanoindentation measurement gave even narrower difference, with hardness values of 1.1 GPa for face 1 and 0.95 GPa for face 2, thus further supporting the above conclusion. The result obtained from nanoindentation contradicts with those from the impulse stimulated light scattering (ISLS) and the Brillouin scattering, but was close to the result predicted by molecular dynamics (MDs) simulation. It is also suggested that the modulus value of 31 GPa obtained from previous micro-indentation measurement may be overestimated.

We demonstrate a femtosecond erbium-doped fibre laser operating in the long wavelength band (L-band) in which topological insulator Bi 2 Se 3 -polyvinyl alcohol film is applied as a saturable absorber. It generates a ~360 fs soliton pulse at 1600 nm with a repetition rate of 35.45 MHz. To the best of our knowledge, this is the shortest pulse duration ever achieved with an L-band design employing Bi 2 Se 3 as a saturable absorber. The result shows topological insulator Bi 2 Se 3 could be a promising candidate to generate L-band ultrafast pulses for practical applications.