Project PTDC/QUI-QUI/116847/2010
Development and Optimization of an All-atom Force Field for Crystalline Organic Compounds
PI: Carlos Eduardo Sabino Bernardes
(2012-2015)
The aim of this project is the development of a model for the accurate prediction of energetic (enthalpies of sublimation) and volumetric properties (densities and unit cell dimensions) of organic compounds in solid state.
The motivations are: (i) despite the large number of enthalpies of sublimation in the literature, they are normally not ascribed to crystal structures and this information is crucial for an accurate development of force fields to be used in Monte Carlo and molecular dynamics (MD) simulations. This detail is even more relevant when the observed differences between enthalpies obtained by different authors are much higher than those observed between polymorphs of the same compound. (ii) The force fields developed up to now for the study of crystal structures were mainly fitted to structural data and, for those where a large number of enthalpies of sublimation were considered, the variation between calculated and experimental data can be as large as 8 kJ/mol. In turn, this difference is greater than that observed between polymorphs, making the use of these models inappropriate for the investigation of microscopic origin of the phase transitions, where an experimental approach is difficult or even impossible. (iii) The force fields mentioned above, were specifically developed for pure organic materials but, as in the case of the pharmaceutical industry, the use of hydrates (or more generically solvates) instead of pure compounds, can be a viable choice in the preparation of an active ingredient. It is, therefore, important the use of computational methods to investigate the properties of these materials.