Theoretical investigations on the nature of interactions in ions (Li+, Na+, Be2+, Mg2+)-water clusters in the gas phase

Abstract

The nature of interaction that is present in ion-water ( M ( H 2 O ) n ) ( M = L i + , N a + , B e 2 + , M g 2 + ) (n = 1–10) clusters are highlighted in the present work. We have used theories of atoms in molecules, symmetry-adapted perturbation, and infrared spectroscopy in the gas phase. The inner structure where the M is surrounded by four H 2 O molecules represent the first shell, followed by the second shell, which is the most stable cluster when n ≥ 4 , for M ( H 2 O ) n ( M = L i + , N a + , B e 2 + ) clusters, and n ≥ 6 for M ( H 2 O ) n ( M = M g 2 + ) cluster. The successive binding energies of M ( H 2 O ) n clusters leads to the conclusion that the affinity for water molecules follows the trend: B e 2 + > M g 2 + > L i + > N a + . The SAPT study demonstrates that the total interaction energy of B e 2 + − water clusters are higher than the other clusters because of high attractive induction and electrostatic energy. The IR spectrum results conclude that in the presence of cations in ( H 2 O ) n clusters blue shifts occur for the hydrogen-bonded O − H stretching mode, and a red shift occurs for the free O − H stretching mode. This investigation contributes significantly to the scientific understanding of these clusters’ bonding interactions, total interaction energy, and successive interaction energy.