- Crystal structure prediction
Crystal structure prediction (CSP) is the calculation of the crystal structures of solids from first principles. Reliable methods of predicting the crystal structure of a compound, based only on its molecular structure, has been a goal of the physical sciences since the 1950s. Computational methods employed include simulated annealing, evolutionary algorithms, distributed multipole analysis, basin hopping, data mining, density functional theory and molecular mechanics.
The crystal structures of simple ionic solids have long been rationalised in terms of Pauling's rules, first set out in 1929 by Linus Pauling. For metals and semiconductors one has different rules involving valence electron concentration. However, prediction and rationalization are rather different things. Most commonly, by crystal structure prediction one understands search for minimum-energy arrangement of the atoms (or, for molecular crystals, of the molecules) in space. The problem has two facets - combinatorial (the "search" problem, in practice most acute for inorganic crystals), and energetic ("ranking", most acute for molecular organic crystals). For complex non-molecular crystals ("search problem"), major recent advances have been the Martonak version of metadynamics  and the Oganov-Glass evolutionary algorithm USPEX. The latter is capable of solving the global optimization problem with up to a few hundred degrees of freedom, while the approach of metadynamics is to reduce all structural variables to a handful of "slow" collective variables (which often works).
The crystal structures of molecular substances, particularly organic compounds, are very hard to predict and rank in stability because the factors that determine them, the intermolecular interactions, are weak and numerous, they act at long range and they have little directionality. Predicting organic crystal structures is important to academic and industrial science, particularly for pharmaceuticals and pigments, where understanding polymorphism is beneficial.
Since 2007, significant progress has been made in the CSP of small organic molecules, with several different methods proving effective. The most widely-discussed method first ranks the energies of all possible crystal structures using a customised MM force field, and finishes by using a dispersion-corrected DFT step to estimate the lattice energy and stability of each short-listed candidate structure.
- A. R. Oganov, ed (2010). Modern Methods of Crystal Structure Prediction. Berlin: Wiley-VCH. ISBN 352740939. http://www.wiley-vch.de/publish/en/books/forthcomingTitles/NT00/3-527-40939-4/?sID=pk4rq15hcr5b64p5huhfk98p80.
- ^ a b G. R. Desiraju (2002). "Cryptic crystallography". Nature Materials 1 (2): 77–79. doi:10.1038/nmat726. PMID 12618812.
- ^ S. M. Woodley, R. Catlow (2008). "Crystal structure prediction from first principles". Nature Materials 7 (12): 937–946. Bibcode 2008NatMa...7..937W. doi:10.1038/nmat2321. PMID 19029928.
- ^ L. Pauling (1929). "The principles determining the structure of complex ionic crystals". Journal of the American Chemical Society 51 (4): 1010–1026. doi:10.1021/ja01379a006.
- ^ Martonak R., Laio A., Parrinello M. (2003). "Predicting crystal structures: The Parrinello-Rahman method revisited". Physical Review Letters 90 (3): 341–53. doi:10.1016/0027-5107(78)90203-8. PMID 75502.
- ^ Martonak R., Donadio D., Oganov A. R., Parrinello M. (2006). "Crystal structure transformations in SiO2 from classical and ab initio metadynamics". Nature Materials 5 (8): 623–626. Bibcode 2006NatMa...5..623M. doi:10.1038/nmat1696. PMID 16845414.
- ^ Oganov, A. R.; Glass, C. W. (2006). "Crystal structure prediction using ab initio evolutionary techniques: principles and applications". Journal of Chemical Physics 124 (10): 8–13. Bibcode 2006JChPh.124x4704O. doi:10.1063/1.2210932. PMID 244704.
- ^ K. Sanderson (2007). "Model predicts structure of crystals". Nature 450 (7171): 771. Bibcode 2007Natur.450..771S. doi:10.1038/450771a. PMID 18063962.
- ^ G. M. Day et al. (2009). "Significant progress in predicting the crystal structures of small organic molecules - a report on the fourth blind test". Acta Crystallographica B 65 (Pt 2): 107–125. doi:10.1107/S0108768109004066. PMID 19299868.
- ^ M. A. Neumann, F. J. J. Leusen, J. Kendrick (2008). "A Major Advance in Crystal Structure Prediction". Angewandte Chemie International Edition 47 (13): 2427–2430. doi:10.1002/anie.200704247. PMID 18288660.
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