Whereas the Ritz variational principle for bound states is a standard text­book example, variational principles for scattering wave functions are still under discussion, especially for composite systems, see the review by Ger — juoy [5]. I will therefore repeat the essential points and refer to [4] for some details. With respect to bound state wave functions of fragments, the

RRGM is nothing but a standard Ritz variation with an ansatz for the wave functions in terms of Gaussian functions, see eqs. (2.33 — 2.36) below. That this expansion converges pretty fast was shown in [4] and is also discussed in chapter 5.1.