Wetting of paracetamol surfaces studied by DMol3-COSMO calculations

Unrelaxed surface models of several relevant faces of the two polymorphic forms of paracetamol were studied by DMol3-conductor-like screening model (COSMO) calculations. This is a computationally expedient first step towards a more complete study of wettability. Our calculated wetting energies for the different faces show a trend consistent with recent contact angle measurements for paracetamol and water. The orthorhombic (001) and the monoclinic (010) surfaces are the most stable ones in the dry state as well as in the wet state. The COSMO wetting energy for these two surfaces agrees very well with the values deduced from experiment. The calculated COSMO wetting energies for the other, more polar, surfaces are higher and get overestimated by the model.