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N.I.Kashirina, V.D.Lakhno, V.V.Sychyov
Electron correlations and spatial configuration of the bipolaron //physica status solidi (b), 2002, v.234, №2, p.563-570

      Bipolaron energy is calculated for various distances between the centers of polarization wells of two polarons with accounting the electron correlations. A singlet bipolaron is stable at a rather high energy of ion binding η ≤ η_m ≈ 0.143, η = ε_∞ / ε₀ (ε_∞ and ε₀ are the high-frequency and static dielectric constants, respectively). The unique energy minimum corresponds to a one-center bipolaron (analog of a helium atom). The bipolaron binding energy constitutes up to 25.8% of a double polaron energy at η → 0. A triplet bipolaron (analog of ortho-helium) is energetically disadvantageous. The one-center configuration of a triplet bipolaron corresponds to a maximum on the distance dependence of the total energy J_Bp(R). The exchange interaction between polarons has antiferromagnetic character. A prediction is made about a possibility of Wigner crystallization of a polaron gas, which occurs with antiferromagnetic ordering in the polaron system.