A cocrystal of 4,4′,5,5′-tetra­nitro-1H,1′H-(2,2′-bi­imidazole)-1,1′-di­amine (DATNBI) and TNT with a molar ratio of 1:2 was synthesized for the first time. The thermal decomposition temperature and mechanical sensitivity of the cocrystal have been greatly improved compared with DATNBI, which provides a certain basic support for the subsequent cocrystal design of DATNBI.

Pure γ polymorphs of 3-chloro- and 3-bromo-trans-cinnamic acids are isostructural and undergo irreversible thermal transformation to different β polymorphs at similar temperatures. A transformation also occurs for the γ form of their solid solution, with a molar ratio close to 1:1, producing a form similar to pure β-3-chloro-trans-cinnamic acid.

Different polymorphic forms of bendamustine hydrochloride, a chemotherapy medication used in the treatment of chronic lymphocytic leukaemia, non-Hodgkin's lymphoma and multiple myeloma, have been found and their relative stabilities established. For three out of the four polymorphs found, the crystalline structures were determined using SC-XRD.

A polymorphic transition was found for 3-[1-(t-but­oxy­carbonyl)­azetidin-3-yl]-1,2-oxazole-4-carb­oxy­lic acid during a grinding process. Metastable and more stable polymorphic structures differ by a molecular conformation and crystal structure organization. Pre-conditions of a polymorphic transition and changes in molecular and crystal structure are studied using experimental and quantum-chemical methods.

Labile multicomponent crystal forms of carbamazepine have been studied with an aim of identifying the structural and surface features that drive the outcome of thermal stress-induced transformations.

Utilizing the Burgers Orientation Relationship and the four-dimensional Frank space, we were able to identify the multiplicity of crystallographically equivalent variants generated by iterative phase transformations (h.c.p. to b.c.c. and vice versa) in pure titanium.

Monohydrate and anhydrate forms of PDA-TPA crystal structures are determined and analysed, and the monohydrate shows favourable stability. The phase transition between the monohydrate and the anhydrate depends strongly on the temperature and water activity, and the larger the value of water activity is, the higher is the transition temperature.

Among the halogen derivatives of N-salicylideneaniline, polymorphs of the dichloro compound A showed the mechanical response of jumping (Forms I and III) and sudden blasting (Form II) upon heating. This difference is ascribed to the layered packing in Forms I and III such that the thermal stress acts in a unidirectional manner while for the corrugated layer structure of Form II the outcome is blasting because the thermal energy dissipates in different directions.

The one-to-one correspondence between a set of cosets of the Mathieu group M₁₁, block sets of the Steiner system S(4, 5, 11) and 11-vertex equi-edged triangulated clusters determines symmetry-allowable transformations between different 11-vertex triangulated clusters as automorphisms of the Steiner system S(4, 5, 11). The transformations can describe local reconstructions corresponding to polymorphic transformations in metals.

This study presents two anhydrous polymorphic forms of psilocin, detailing their crystal structures and hydrogen-bonding differences, with Form II introducing a novel conformation and whole-mol­ecule disorder.