  Motivated by experimental hints for supersolidity in Helium-4, we perform
Monte Carlo simulations of vacancies and interstitials in a classical two-and
three-dimensional Lennard-Jones solid. We confirm a strong binding energy of
vacancies which is of the order of Lennard-Jones attraction. This is
reminiscent of what has been found for vacancies in Quantum Monte Carlo
simulations. In addition, we find a strong attraction and large binding energy
of interstitials in two-dimensional simulations. This is mainly due to the
formation of a pair of dislocations by clustering interstitials, in which
minimizes the elastic deformation energy. We interpret the results in light of
the properties of Helium-4.
