Ab initio method for calculating total cross sections.

A method for calculating total cross sections without formally including nonelastic channels is presented. The idea is to use a one channel [ital T]-matrix variational principle with a complex correlation function. The derived [ital T] matrix is therefore not unitary: Elastic scattering is calculated from [vert bar][ital T][vert bar][sup 2], but total scattering is derived from the imaginary part of [ital T] using the optical theorem. The method is applied to the spherically symmetric model of electron-hydrogen scattering. No spurious structure arises; results for [sigma][sub el] and [sigma][sub total] are in excellent agreement with calculations of Callaway and Oza. The method has wide potential applicability.