Density-functional study of hydration of ammonium in water clusters

The structure and hydration energy of small water clusters containing an am monium ion are investigated within density functional theory by using the B ecke-Lee-Yang-Parr (BLYP) generalized gradient corrections to the local den sity approximation to the exchange and correlation energy, norm-conserving pseudopotentials, and a plane-wave expansion of Kohn-Sham orbitals. The cal culated hydration energies are in good agreement with experimental data and with available quantum chemical calculations. The result of this study fur nishes us with further evidence of the ability of the BLYP functional to pr ovide a good description of hydrated systems. (C) 1999 American Institute o f Physics. [S0021-9606(99)31009-6].