Adsorption of water on sodium chloride surfaces: electrostatics - guided ab initio studies

Water adsorption is studied on medium-sized clusters of sodium chloride representing (100) and (110) surfaces at the ab initio level. Topographical features of molecular electrostatic potential (MESP) have been employed for predicting the potent sites for binding of one to four water molecules on these surfaces. Such guess geometries are initially optimized using an electrostatics-based model, electrostatic potential for intermolecular complexation (EPIC) and further at the Hartree-Fock and B3LYP/6-31G(d, p) levels. The corresponding interaction energies are examined for assessing co-operative binding effects. The geometry and interaction energy of four water molecules adsorbed on NaCl(100) clearly brings out the co-operative binding among the water molecules. Further, water binding to (110) surface is stronger than that with (100) surface. This is also in confirmation with the electrostatic properties of (110) surface. Many-body decomposition analysis brings out the stronger interaction between NaCl clusters with water molecules vis-a-vis water-water interaction

Structure, reactivity and aromaticity of acenes and their BN analogues: a density functional and electrostatic investigation

Density functional calculations have been carried out on a series of linearly annelated acenes and their BN analogues. Even though borazine shows aromatic and reactivity behavior parallel with that of benzene, its condensed derivatives show patterns different from those of their hydrocarbon analogues. Nucleus independent chemical shift (NICS) values in acenes suggest that the aromaticity of the inner rings is more than that of benzene, whereas in BN-acenes there is no substantial change in the aromaticity of the individual rings. Molecular electrostatic potential (MESP) is employed to obtain further insights into the bonding and reactivity trends for these systems. The MESP topography patterns of acenes and BN-acenes are substantially different, with BN-acenes showing more localized p electron features compared to those of acenes. The MESP values at the critical points (CPs) indicate overall lowering of aromaticity in these annelated systems. However, this change is gradual among the BN-acenes