Systematic screening forktype phase transitions – general approach and positive example for a binuclear Cu(ii) paddlewheel structure

Abstract

How to screen for k type phase transitions? Pseudo symmetry in reciprocal space represents a successful answer.

Melting pseudosymmetry and thermal expansion in 3-benzoylpropionic acid

“…A recent CSD data-mining study revealed several low-temperature structures which undergo k -transitions into a more symmetric phase upon heating, associated with the loss or change of pseudosymmetry. 52 It seems that in multiple Z ′ > 1 crystals, including BPA, they are indeed the only thermodynamically stable forms at low temperatures and not merely “fossil relics” of the nucleation process, as generally crystallizations are carried out, instead, around room temperature, and produce mostly Z ≤ 1 structures.…”

“…This journal is © The Royal Society of 2023 low-temperature structures which undergo k-transitions into a more symmetric phase upon heating, associated with the loss or change of pseudosymmetry. 52 It seems that in multiple Z′ > 1 crystals, including BPA, they are indeed the only thermodynamically stable forms at low temperatures and not merely "fossil relics" of the nucleation process, as generally crystallizations are carried out, instead, around room temperature, and produce mostly Z ≤ 1 structures. One of the parameters which can pinpoint the structural similarity between the molecules is the torsional angle (τ) formed through a carboxylic carbon and the propyl chain (C1-C2-C3-C4).…”

Temperature-Resolved Anisotropic Displacement Parameters from Theory and Experiment: A Case Study

“…The superior instrumentation available nowadays for diffraction experiments clearly facilitates systematic temperature-dependent studies [40], e.g., dedicated to molecular motion [41] or phase transitions [42,43] in molecular crystals. As a result of enormous progress in computer hard-and software, mobility in such molecular solids may also be assessed by theoretical methods [44,45].…”