Inverse multislice calculations: a new method for solving complex structures
Hayden Faulkner · Acta Crystallographica Section A Foundations of Crystallography · 2008
A comprehensive computational strategy for the prediction of crystal structures is presented that has scored an unprecedented 4 in 4 success rate at the 2007 CCDC blind test on crystal structure prediction [1].Key components of the new approach, implemented in the GRACE software package, are a hybrid method for the accurate calculation of lattice energies, a robust procedure for the parameterization of tailor-made force fields and a novel approach for crystal structure generation.The hybrid method combines DFT calculations by means of the VASP program with an empirical van der Waals correction.It is used for the final lattice energy ranking and acts as a reference standard for force field parameterization.A tailormade force field is derived for each molecule to be considered and used for crystal structure generation as well as for the preparation of second derivative matrices for the final lattice energy optimization with the hybrid method.Based on the known statistical deviation between the tailor-made force field and the hybrid method, a shortlist of crystal structures from a small energy window is selected for the final lattice energy optimization and ranking.In addition to the blind test results, validation studies for 15 organic molecules are presented, including ethane, ethylene, acetylene, methanol, urea, acetic acid, cyclohexane-1,4-dione, paracetamol, CCDC blind test molecules I to VI and a pharmaceutical compound for which crystal structures have been predicted in a blind test fashion.17 out of the 18 experimentally observed crystal forms of these molecules are found among the first two most stable predicted crystal structures.