Calculation of the f.i.r. absorption frequencies of polyethylene using a proved semiempirical potential function

A potential function successful in describing the properties of isolated chains of several polymers as well as crystal properties of polyethylene is applied to calculate frequencies of lattice modes of this polymer. The B_1u and B_2u frequencies are determined as 86 and 105 cm^?1, respectively, for the crystal at T = OK. These values are compared with the extrapolated frequencies from temperature dependent f.i.r. absorption spectrum of linear PE (6011 L) measured by Frank et al. The values are 83 and 108 cm^?1, respectively. An influence of the setting angle to the transition moment is discussed.