On the structure of anionic clusters in liquid CO2 and photodisintegration of (CO2) n − clusters

Abstract

The physicochemical properties of ëé 2 solutions in the supercritical state (sc-ëé 2 ) have been extensively studied in the past decade [1][2][3][4]. This interest stems from the fact that sc-ëé 2 is an environmentally safe solvent that substitutes for toxic nonpolar solvents, such as acetone, methanol, and toluene, in industry. In addition, sc-ëé 2 is a candidate for a coolant for nuclear reactors. A specific feature of sc-CO 2 is the formation of clusters of anions with the number of particles n = 2, 3, 4, 7, 13, or more [3]. The quasi-free electron is localized in the potential well arising from the interaction of the electron with the surrounding atoms of ëé 2 molecules. This solvated electron is treated as an anion with a characteristic radius embedded in a solvation shell with a complex structure. The presence of such charged clusters strongly affects the adsorption and transfer processes and the chemical reactivity of reagents in solutions of sc-ëé 2 . Although numerous studies have been focused on the behavior of the electron in liquid systems, effects related to the limitation of the volume or number of particles in the system under consideration taking into account the structural characteristics of molecular clusters are still poorly understood. Such effects are of importance for clusters; in particular, they can lead to the formation of the localized surface electron state. In this work, we considered the localized electron state on the surface of molecular clusters with n = 7 and 13 taking into account their spatial structures. The structures of the most stable anionic clusters were suggested, and the photodisintegration cross sections of these clusters were calculated. Based on analysis of the symmetry and magic numbers of the clusters, we suggested dodecahedral and icosahedral structures of the anionic clusters and , respectively. Both clusters have spherical symmetry, which makes it possible to use the Dirac bubble model potential [4] in calculations of the electron-cluster interaction.) 13 -Analysis of the spatial structures of clusters provides rich information on the interaction of their constituent atoms and molecules and allows one to select appropriate model potentials in calculations of their properties. Shkrob and Sauer [3] suggested that the nucleus of the atomic clusters with n ≤ 6 and n ≥ 14 is the dimer, whereas, in the clusters with 6 < n < 14, the nucleus is the ion, which interacts with surrounding molecules with a binding energy of 0.22 eV per molecule. Any informational, mathematical, physical, crystal, and biological structures are based on polyhedra; therefore, it is reasonable to assume the formation of more or less regular structures in sc-ëé 2 . Indeed, ab initio calculations show that ëé 2 trimers and tetramers have the C 2 v symmetry and a T-shaped configuration [5].The calculations of the topological structures of clusters in various gases [6] show that, in the case of van der Waals interactions, noble gas clusters containing 7, 13, or 16 particles correspond to their stabl...