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Speciale, 3. modul, 2013, id:285
Vejleder:Jeppe C. Dyre
Findes på RUb:Ja
English abstract
It has been shown [1] that for liquids exhibiting strong correlation between its NVT virial and potential energy equilibrium fluctuations, one can, to a good approximation, define isomorphic curves in the density-temperature phase diagram, along which structure, dynamics, excess entropy, heat capacity etc. are all invariant. We investigate this behavior via MD-simulations in the FCC-crystalline state for Lennard-Jones systems and show that the strong correlation here is even more pronounced than for the liquid. This implies that isomorphic curves exist in the crystal phase, as well. We confirm this by studying the following predicted invariance: (1) The structure via the radial distribution function and structure factor, (2) short-ranged dynamics via the velocity autocorrelation function, (3) long-ranged dynamics via mean-square displacement of crystal vacancies, (4) aging via the relaxations of the system after instantaneous jumps between isomorphic state points. In all cases we compare the results with similar results along isochors and isotherms. In addition we investigate sodium-chloride in the crystal phase modeled by a potential consisting of a Lennard-Jones and a Coulomb term in a FCC structure. This system exhibits correlations just below the limit of strong correlations, and as a consequence has less well-defined isomorphs.

Database opslag den: 25-01-2021