Ab initio Calculation of the Conformations and Vibrational Spectra of 2-Phenylbutane

Abstract

Molecules with internal degrees of rotation are of particular interest to understand the behavior of synthetic or natural polymers. With the extremely rapid increase in floating point performance of modern computers we are able to calculate a subspace of the Born-Oppenheimer hypersphere for quite large molecules with ab initio methods. We choose 2-Phenylbutane as an elementary model for Polystyrene (PS), because it possesses two internal degrees of freedom, that are highly relevant for PS. These are the rotation of the benzene ring and the chain like motion of the ethylgroup.