Structure of the Wave Function of Crystalline 4He
The nature of the wave function for quantum crystals has been an outstanding problem for some time. Although a Jastrow product wave function gives a qualitatively correct description of the liquid, and although such a wave function can describe a crystal, the result is in serious disagreement with experiment. The standard treatment is to construct a lattice and directly couple the particles to its sites. Although this gives fair numerical agreement with some crystal properties, it is at the expense of breaking the Bose symmetry of the crystal. We introduce here a new class of trial wave functions that are symmetric under particle exchange. They give a lower variational energy than, and have properties comparable with those given by trial functions in which atoms are explicitly localized.
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