High-pressure experimental study on Rb₂S: antifluorite to Ni₂In-type phase transitions

Rubidium sulfide, Rb₂S, with an antifluorite-type structure at 1 bar, has been studied up to 8 GPa using angle-dispersive X-ray diffraction in a diamond–anvil cell. Two different high-pressure phases have been characterized: (i) an anticotunnite-type structure (P > 0.7 GPa) and (ii) an Ni₂In-type structure (P > 2.6 GPa).

Disorder of (NH₄)₃H(SO₄)₂ in the high-temperature phase I

The disordered crystal structure of (NH₄)₃H(SO₄)₂ in the high-temperature phase I at 413 K was studied using single-crystal neutron diffraction.

Structural phase transitions in tetra(iso­propyl­ammonium) deca­chlorotricadmate(II), [(CH₃)₂CHNH₃]₄Cd₃Cl₁₀, crystal with a two-dimensional cadmium(II) halide network

Single crystals of tetra(isopropylammonium) decachlorotricadmate (II) with their unique two-dimensional [Cd₃Cl₁₀] network exhibit rich polymorphism in a narrow temperature range (phase transitions at 353, 294 and 259 K). The mechanisms of these transformations are discussed.

Detailed study of the phase transition in [Ni(H₂O)₆](NO₃)₂·(15-crown-5)·H₂O and analysis in terms of mean-field theory

The phase transition between 190 and 200 K in [Ni(H₂O)₆](NO₃)₂·(15-crown-5)·H₂O has been followed by determining the structure at 22 temperatures in the range 90−273 K. An attempt has been made to describe the transition using mean-field theory.

Charge-density analysis in polymorphs of urea–barbituric acid co-crystals

Experimental charge-density studies were performed for two of the three polymorphic modifications of barbituric acid–urea co-crystals. The topological properties of intermolecular interactions confirmed the tendency of barbituric acid to adopt different mesomeric forms in the polymorphs. The mesomeric forms influence the various systems of the observed hydrogen bonds.

Predicted and experimental crystal structures of ethyl-tert-butyl ether

Possible crystal structures of ethyl-tert-butyl ether were predicted by global lattice-energy minimizations. The densest calculated structure corresponds to the experimental one which was determined from low-temperature X-ray powder data.

Solid-state transformations in the β-form of chlorpropamide on cooling to 100 K

A single-crystal X-ray diffraction study in the temperature range 100–300 K has revealed two reversible non-destructive phase transitions with a continuous decrease in volume per molecule in the β-form of chlorpropamide: β (Pbcn, Z′ = 1)  β^II (P2/c, Z′ = 2)  β^III (P2/n, a′  =  2a, Z′ = 4); the sequence corresponds to cooling.

Seven hexa­methylene­tetramine (HMTA) complexes with mono- and di­carboxylic acids: analysis of packing modes of HMTA complexes in the literature

The types of packing of hexamethylenetetramine (HMTA) complexes, either co-crystals or salts, are explained with regard to the molecular shape of the HMTA molecule and the number and type of functional groups of the partner molecule, with which the HMTA molecule interacts. One-dimensional assemblies featuring zigzag-shaped chains are derived from the tetrahedral arrangement of the N atoms on the HMTA.