Portal de Periódicos da CAPES

Quantum Monte Carlo studies of vibrational states in molecules and clusters

1991; Elsevier BV; Volume: 204; Issue: 4 Linguagem: Inglês

10.1016/0370-1573(91)90136-a

1873-6270

Martin A. Suhm, R.O. Watts,

Advanced NMR Techniques and Applications

The interaction between ammonium ions and water has been studied previously via molecular dynamics. However, the nuclear quantum effect phenomenon did not receive sufficient consideration therein. In this study, we report the ab initio path integral molecular dynamics (PIMD) simulations of the isotopologues of NH4+(H2O), that is, NH4+(H2O), ND4+(D2O), and NT4+(T2O), as well as the classical MD simulations. We found that the intermolecular distance does not change monotonically. Even though the nuclear quantum effect shortens the overall intermolecular distance (N–O atoms), the distance for NH4+(H2O) is longer than that for NT4+(T2O). Two dimensional distributions of the binding energies with the contour lines were constructed to assess this unusual quantum behavior. We find that the elongation of the covalent bond increases the binding energy, while the quantum fluctuation of the O–N–Hb bond angle decreases it. The bond length is determined by the delicate balance of such competing quantum effects.