ADIABATIC THEORY FOR THE BIPOLARON

Comments are given on the application of the Bogoliubov-Tyablikov appr oach to the bipolaron problem in a recent paper by Lakhno [Phys. Rev. B 51, 3512 (1995)]. This author believes that his model (1) is the tra nslation-invariant adiabatic theory of bipolarons and (2) gives asympt otically exact solutions in the adiabatic limit while the other approa ches are considered as either phenomenological or variational in natur e. Numerical results by Lakhno are in contradiction with all other pap ers published on the subject because his model leads to much lower ene rgies. Thus, the author concludes that bipolarons ''are more stable th an was considered before.'' We prove that both the analytical and the numerical results presented by Lakhno are wrong.