Abstract
The frozen-orbital (FO) method previously proposed by Gauyacq (1978) to generate diabatic molecular orbitals is improved by the introduction of distortion effects. The basic idea of this 'distorted frozen-orbital' (DFO) method is to calculate variationally the different diabatic orbitals in different orthogonal subspaces defined with the help of the frozen-orbital method. Application to the Ne-Ne collisional system indeed shows that the major defects of the FO method are removed. Cross section calculations are performed in the DFO basis set in order to compare its predictions with those of the previous diabatic basis sets.