Cluster Ions in Vapour over Calcium Dichloride: Theoretical Study of Geometrical Structure and Vibrational Spectra

Geometrical structure and vibrational spectra for CaCl3–, Ca2Cl3+, Ca3Cl5+, Ca4Cl7+, and Ca5Cl9+ ions have been studied by employing density functional theory and the second order Møller–Plesset perturbation theory. The equilibrium geometrical structures are as follows: the planar D3h for CaCl3–, triple-bridged bipyramid D3h for Ca2Cl3+, hexa-bridged bipyramid D3h for Ca3Cl5+, polyhedral C2v for Ca4Cl7+, and polyhedral D3h for Ca5Cl9+. No isomers have been confirmed to exist.