CrystalOptimizer: An Efficient Algorithm for Lattice Energy Minimization of Organic Crystals Using Isolated‐Molecule Quantum Mechanical Calculations

Polymorph Identification for Flexible Molecules: Linear Regression Analysis of Experimental and Calculated Solution- and Solid-State NMR Data

“…The integration of solid-state NMR data and ab initio calculations of NMR parameters in NMR crystallography presents a valuable approach for determining crystal structures. − ,− Requiring a good starting structural model that is geometry optimized before the calculation of NMR parameters, NMR crystallography is now widely employed in academia and increasingly in industry, particularly to refine and improve the quality of structures derived from both single-crystal and powder X-ray diffraction data. − ,− ,,, NMR crystallography can also be used to determine crystal structures de novo without X-ray diffraction data by finding the model from a CSP ,,− campaign whose calculated properties are most consistent with the experimental NMR data. ,− ,,,,− Chemical shifts for proposed model structures are calculated, usually using the gauge-including projector augmented wave (GIPAW) method, − and compared directly with experimentally measured solid-state NMR chemical shifts, with only the correct model expected to pass the given thresholds of agreement for the root mean squared error (RMSE). ,,, …”

“…Providing structural models for NMR crystallography by CSP is, however, computationally expensive because of the number of possible ways molecules can be packed together . Conformational polymorphism, where a different torsion angle value exists for a flexible part of a molecular component, adds additional complexity, requiring separate calculation runs for each putative conformation. ,, When several rotatable bonds are present, an extremely large set of likely conformations is often generated, with an even greater set of structural models as each conformation’s packing is explored. , Yet more structural models are generated by CSP when the number of molecules in the asymmetric unit cell is greater than one. , …”

Repulsion–dispersion parameters for the modelling of organic molecular crystals containing N, O, S and Cl

“…In the CSP approach developed in our group, 24 different energy models are used for the global search step in which thousands of possible structures are generated (CrystalPredictor 16,17,25,26 ) and in the renement step in which the ranking of structures is nalized (CrystalOptimizer 27,28 ). Recent developments in the model for the global search 16,17 have led to signicant improvements in the accuracy of the force elds for large exible molecules (such as molecule XXVI in the sixth blind test); in general, all experimentally-relevant structures are typically identied within 20 kJ mol À1 of the global minimum and carried through to the renement stage.…”

“…16,17 The latter requires a higher degree of accuracy in the lattice energy. The intramolecular energy is calculated using local approximate models derived from the isolated-molecule ab initio energy 27 computed at a chosen level of theory. The intermolecular energy is derived by combining electrostatic interactions represented by distributed multipoles 15,29,30 derived from the isolated molecule charge density calculated at the same level of theory, and repulsiondispersion interactions modelled by an empirical exp-6 potential with parameters taken from the literature such as the FIT potential, [31][32][33][34][35][36][37] W01 (ref.…”