Crystal to Glass Transition and its Relation to Melting

[摘要] This work contributes to the understanding of thermodynamic aspects and microscopic mechanisms of the crystal to glass transition and its relationship to melting. The topological order to disorder transition was investigated primarily in a model system consisting of Lennard-Jones binary solid solutions via molecular dynamics simulations. Under constant temperature and pressure, thermodynamic properties and structures of the solid solutions are mainly determined by solute/solvent atomic size difference and solute concentration. At a critical atomic size difference and/or concentration, the transition was found to occur with extremely small latent heat and density change, but large softening of shear elastic constants. Microscopic details such as atomic configuration show that the transition is induced by collective topological defects created by differences in atomic sizes of the solute and solvent atoms. The inhomogeneity in atomic displacements caused by these defects was shown to be directly responsible forcrossover of the transition from a first order transition to a continuous one. The fundamental difference between melting and the crystal to glass transition was demonstrated by their thermodynamic, dynamic, and structural behavior under different kinetic environments. It was shown that melting is intrinsically a first order transition, whereas crystal to glass transition can occur in a variety of forms that are crucially dependent on the kinetic constraints imposed on the solid phases.

[发布机构] University:California Institute of Technology;Department:Engineering and Applied Science

[关键词] Applied Physics