The method of molecular dynamics simulation has been used to investigate the mechanism of phase decay of a Lennard-Jones fcc crystal close to the boundary of 'ideal strength'. The attainability of states where the isothermal bulk modulus K-T = rho(partial derivative p/partial derivative p)(T) = 0 and K-T < 0 has been demonstrated at negative pressures. It has been shown that the decay of the crystal phase proceeds by different activation mechanisms: (i) by the formation of voids at temperatures below that of the endpoint of the melting line and (ii) by liquid-phase critical nuclei formation above this temperature. (C) 2015 Elsevier B.V. All rights reserved.