Quantum fluid-solid transition in a simple variational approach II. Effects of overlap and exchange
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A variety of anomalous (non-plane-wave) single-particle permanent (determinant) states consisting of localized and orthonormal but mutually overlapping orbitals, are found to have lower energy than the normal (plane-wave) states. This is shown to occur in a considerable region of the coupling-constant vs density plane, for simple repulsive interactions. New effects, attributable to the presence of overlap (and thus exchange) appear. Among these are a relatively stable antiferromagnetic liquid state emerging before the crystalline state. Also, for spinless bosons or fermions, the density region of fluid stability no longer shrinks to zero even for arbitrarily strong coupling. Effects of attractive forces are also treated. © 1975.