Abstract
Calculations are performed for two-, three-, and four-particle exchange in the quantum crystal of bcc solid3He. The quasiclassical approximation is used to find the tunneling path in the space of all atomic coordinates of the crystal. Effective potential energy is introduced by means of elasticity theory and the Lennard-Jones anharmonic interaction for exchanging atoms and their nearest neighbors. The two leading terms in the expansion of the logarithm of the exchange integrals in powers of the quasiclassical parameter given by the ratio of the zero oscillation amplitude to the lattice spacing are calculated. It is shown that all three exchange integrals are of the same order of magnitude.
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