Displacement field and elastic constants in nonideal crystals
نویسندگان
چکیده
In this work a periodic crystal with point defects is described in the framework of linear-response theory for broken-symmetry states using correlation functions and Zwanzig-Mori equations. The main results are microscopic expressions for the elastic constants and for the coarse-grained density, point-defect density, and displacement field, which are valid in real crystals, where vacancies and interstitials are present. The coarsegrained density field differs from the small wave-vector limit of the microscopic density. In the longwavelength limit, we recover the phenomenological description of elasticity theory including the defect density.
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