Ab InitioStudy on Structures and Vibrational Spectra of M⁺(H₂O)Ar₂(M = Cu, Au)

Abstract

Previous investigations have shown that it is difficult to acquire the infrared (IR) spectra of M þ (H 2 O) (M ¼ Cu, Au) using a single IR photon by attaching an Ar atom to M þ (H 2 O). To explore whether the IR spectra can be obtained using the two Ar atoms tagging method, the geometrical structures, IR spectra and interaction energies are investigated in detail by ab initio electronic structure calculations for M þ (H 2 O)Ar 2 (M ¼ Cu, Au) complexes. Two conceivable isomeric structures are found, which result from different binding sites for two Ar atoms. CCSD(T) calculations predict that two Ar atoms are most likely to attach to Cu þ for the Cu þ (H 2 O)Ar 2 complex, while the Au þ (H 2 O)Ar 2 complex prefers the isomer in which one Ar atom attaches to an H atom of the H 2 O molecule and the other one is bound to Au þ . Moreover, the calculated binding energies of the second Ar atom are smaller than the IR photon energy, and so it is possible to obtain the IR spectra for both Cu and Au species. The changes in the spectra caused by the attachment of Ar atoms to M þ (H 2 O) are discussed.