Energetic materials: variable-temperature crystal structures of γ- and ∊-HNIW polymorphs

Abstract

Crystals of -and 4-hexanitrohexaazaisowurtzitane (-and 4-HNIW, space group P2 1 /n for both crystals) have been investigated in the 100±298 K temperature range using single-crystal X-ray diffraction techniques. Temperature-dependent changes of their crystal lattices have been evaluated from the second-rank thermal expansion tensors. Both lattices undergo anisotropic thermal expansion, that of -HNIW being more anisotropic than that of the 4 phase. Comparison with previously reported predictions from molecular dynamics calculations indicates signi®cant differences. Although there are many short (less than van der Waals) intermolecular interactions in both polymorphs, there is no obvious relationship between the short distances and the difference in thermal expansion behavior. Non-linear temperature dependence of the atomic displacement parameters is indicative of anharmonicity of the crystal mean ®eld potential.

Polymorphism in hexanitrohexaazaisowurtzitane crystallized from solution

“…Five conformational polymorphs and an hydrate form have been found so far [18][19][20][21], but only four directly produced in many HNIW synthesis techniques and need recrystallization [22][23][24][25]. However, there often exists other polymorphs in form e from recrystallization, which will decrease the density, enhance the sensitivity and then reduce the performance of HNIW.…”

A new polymorph of dichlorido(1,10-phenanthroline)platinum(II)

“…Differences in the crystalline arrangement can affect the solubility or the bioavailability of a drug [1][2][3][4]; moreover, the least stable phase, at room temperature, generally coincides with the most efficient pharmaceutical form. Polymorphs are present in explosives [5,6] and in pigments; in the latter substances the different solid phases may differ in resistance to heat and light irradiation with severe effects on the commercial value of one phase over the other [7].…”

Pushing the limits of energetic materials – the synthesis and characterization of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate

“…1 Representation of the solid state molecular structure of TKX 50 at 100 K. Thermal ellipsoids are drawn at the 50% probability level; symmetry codes: (i) 2 x, y, 2 z; (ii) x, 0.5 y, 0.5 + z; and (iii) 1 + x, 0.5 y, 0.5 + z. 24 1.858 (90 K) 26 1.944 (100 K) 28 2.083 (100 K) 29 1.918 (100 K) 30 1.648 (298 K) 25 1.806 (298 K) 27 1.904 (298 K) 28 2.035 (298 K) 29 vented. A defined volume of 25 mL of the compound is loaded into the flanged steel tube and a threaded collar is slipped onto the tube from below.…”