Structures and Stabilities of (CaO)n Nanoclusters

The global energy minima structures for (CaO)n for n ≤ 40 were predicted using density functional theory. The cubic structures are found to be the lowest energy isomers for most (CaO)n, n ≥ 4. A fragment-based structure-energy relationship model gave an excellent fit for the calculated total energy. Based on the fitting results, the bulk limit for the normalized clustering energy for (CaO)n particles was predicted to be 157.8 kcal/mol for the enthalpy at 298 K, in good agreement with the experimental/computational bulk value of 156.5 kcal/mol. A (CaO)n nanoparticle with a size of 10 nm is predicted to have a CaO binding energy close to that of the bulk crystal. The infinite chain limit for normalized clustering energy for various one-dimensional (1-D) cubic nanoparticle series was also obtained. The surface energy densities were predicted to be 62 kcal/mol per CaO for the 3-coordinate corner fragment, 30 kcal/mol per CaO for the 4-coordinate edge fragment, and 11 kcal/mol per CaO for the 5-coordinate face...