Molecular Structures and Potential Energy Surfaces for IHI-·Arn (n = 1−7)

Abstract

<p>This study reports second-order perturbation (MP2) theory predictions of the optimized structures and relative energies for IHI-·Ar<em>n</em> (<em>n</em> = 1−7) complexes. For <em>n</em> = 1−6, the lowest energy structure has all <em>n</em> Ar atoms forming a partial ring in the plane that is perpendicular to and bisects the IHI- axis. The ring is closed at <em>n</em> = 6, and for <em>n</em> = 7, one of the Ar atoms moves into a second ring. Analysis of the geometrical parameters and three-dimensional MP2 molecular electrostatic potentials (MEP) is used to determine why the ring structure is lowest in energy for <em>n</em> = 1−6, but not for <em>n</em> = 7. Based on the MEP, it is concluded that Ar atoms tend to distribute in regions of low electron density that exist in the plane perpendicular to and bisecting the IHI- axis. Hence, the global minimum for all <em>n</em> < 7 is a ring structure in this plane. For <em>n</em> = 7, steric effects force an Ar atom into a new ring.</p>