Acta Crystallographica Section A Foundations and Advances, Год журнала: 2023, Номер 79(a2), С. C481 - C481

Опубликована: Авг. 22, 2023

The concept of "archetype structure" links disorder to polymorphism and solid solutions [1], since non-disordered archetypes obtained experimentally in pure form, i.e., without disorder, would be considered polymorphs, or different components a solution.Archetype structures also provide rationale why occurs based on energy [2] (together with other relevant criteria [3]).Further applicability is crystal solvent special positions.These systems crystallize as an overlay archetypes, usually through adding translation symmetry when the itself has higher molecular symmetry.A lowersymmetry subgroup found average structure (an aristotype [4]) then observed for archetype.Several examples from drug subset [5] CSD were evaluated will presented.The directly leads new practice modelling experimental least-squares (LSQ) refinement, where structural archetype contributing composed components.In this practice, are initially extracted disordered -as if each component was not disordered-to input separate quantum mechanical (QM) optimization.When subsequently recombining optimized atomic coordinates into model, overlapping atoms permit LSQ refinement their position displacement parameters due parameter correlation (depending resolution extent pseudo-symmetry).Therefore, we incorporate structure-specific restraints QM geometry optimization entire archetype, rather than only atoms, assigned PART.To generate 1,2 (bond distance DFIX) 1,3 angle DANG) avoiding hard EXYZ constraints proximate rely results molecule-in-cluster (MIC) [6]; however do share (ADPs) via EADP constraints.We convert computational output SHELXL program BAERLAUCH [7].Starting (single-crystal X-ray, electron, powder diffraction) subdivided MIC optimisation asymmetric unit content cluster molecules does but permits crossvalidation model chemical results.It that forming within very tight bounds, RT, T being temperature R ideal gas constant [2].Another aspect it makes series comparable data quality encountered.Overall structures" useful crystallographic point view, link energy, essence crystallography.To accurately quantify differences support energetic equality (or similarity) underlies symmetry, use density functional theory dispersion correction (DFT-D).Such DFT-D energies can e.g.be ONIOM [8] partitioning.Ultimately energy-based analysis using real life application.It example guide practical applications pharmaceutical industry, illustrated predicting cocrystal formation guiding screening [9].

Язык: Английский