# ANALYSES OF VIBRATIONS OF $Ar_{n}$ AND $Ar_{n}CO_{2}$ CLUSTERS BY MOLECULAR DYNAMICS CALCULATION

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 Title: ANALYSES OF VIBRATIONS OF $Ar_{n}$ AND $Ar_{n}CO_{2}$ CLUSTERS BY MOLECULAR DYNAMICS CALCULATION Creators: Ozaki, Y.; Ichihashi, M.; Kondow, T.; Kuchitsu, Kozo Issue Date: 1996 Publisher: Ohio State University Abstract: Previously we analyzed intracluster vibrational motions of $Ar_{n}$, $n_{13}-55$, clusters by use of molecular dynamics $method^{a}$. It was shown that a number of collective vibrations were excited. The vibrations were assigned to breathing, quadruple spheroidal and quadruple torsional vibrations corresponding to the modes of a dense sphere with the radius of $Ar_{n}$ and the phonon velocities in solid Ar. Such vibrations were observed for Ar Clusters by the energy loss of colliding He $atoms ^{b}$. The frequencies of these vibrations were found to decrease with the incressing cluster size, suggesting that these vibrational motions are new physical properties of clusters obeying a scaling law. In this work, the motions of Ar atoms and $CO_{2}$ molecule in $Ar_{n}CO_{2}$ cluster produced by addition of $CO_{2}$ to the surface of $Ar_{n}$ cluster, are simulated by use of the classical molecular dynamics method. The potential is calculated by overlapping two-body Lennard-Jones potentials, where an anisotropic potential is used for the Ar-$CO_{2}$ interection. By extracting the breathing and quadruple spheroidal vibrations, the frequencies of these modes are calculated to be: e.g., 33 and $20 cm^{-1}$, respectively, for $Ar_{13}CO_{2}$. These values are almost indentical to those for $Ar_{13}$. This indicates that the addition of $CO_{2}$ causes little effect on the vibration of $Ar_{13}$ when the $CO_{2}$ molecule is on the surface of $Ar_{13}$. Cluster-temperature and cluster-size dependence of the frequencies will be presented. Description: $^{a}$Y. Ozaki, M. Ichihashi and T. Kondow, Chem. Phys. Lett. 182, 57 (1991); ibid. 188, 555 (1992). $^{b}$C. Buck and R. Krohne, Phys. Rev. Lett. 73, 947 (1994). Author Institution: Department of Chemistry, Faculty of Science, Josai University; Department of Chemistry, School of Science, The University of Tokyo; Department of Chemistry, Faculty of Science, Josai University URI: http://hdl.handle.net/1811/13629 Other Identifiers: 1996-TC-10