jp7b09062_si_001.pdf (4.13 MB)

# Structures and Stabilities of (CaO)_{n} Nanoclusters

journal contribution

posted on 2017-09-26, 00:00 authored by Mingyang Chen, K. Sahan Thanthiriwatte, David A. DixonThe
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*fragment. On the basis of the values of the parity sum for the atom counts for the cube’s edges in three dimensions, cubic (CaO)_{n}nanoclusters can be classified into three types with different geometries. Although no significant difference in stability was found for different types of cubic (CaO)_{n}, several electronic properties of the cubic (CaO)_{n}are related to the parity sum at small*n*. The type-2 (CaO)_{n}clusters and ultrasmall particles in the shape of the odd × odd × even cube, with a parity sum of 2, exhibit unique electronic properties. The type-2 3 × 3 ×*m*1-D nanoparticle series has the lowest HOMO–LUMO excitation energy among all of the 1-D nanoparticle series at all particle sizes: 2.51 eV for the 3 × 3 × 4 cube and 0.70 eV for the 3 × 3 × 18 cube. The patterns for the variation of*E*_{g}during the 1-D layer-wise growth of (CaO)_{n}were analyzed.