Modeling the annealing and thermal stability of silver dental amalgam.

Effect of heat treatment on the structure and thermal properties of silver-copper dental amalgam (Ag-Cu/Hg) was investigated by means of Monte Carlo (MC) simulation. Simulated pair correlation functions in the framework of MC algorithm form the basis for a diverse analysis of the amalgam annealed up to 2893 K. As heat treatment increases, structural properties remain essentially unchanged up to 1093 K, beyond which, the properties are deteriorated. Phase separation in the context of homo-coordination and segregation of Ag-Cu alloy is characterized as the annealing of amalgam alloy is proceeded. Thus, the amalgam alloy could also maintain a microstructural phase and a structural strength around this temperature, consistent with the annealing reported experimentally. These findings provide insights into amalgam industrial technology, setting amalgamation process, Hg release in dental clinics, and basic information appreciated in the dentistry industry and partnership in forensic science. Graphical abstract Thermal stability of the homogeneous amalgam (Ag-Cu/Hg) is studied up to 2893 K where a phase separation and structural alteration is noted above 1093 and Hg phase segregates into a domain different from Ag-Cu alloy domain.

Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion.

Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear and nonlinear regimes. For both systems, when represented in reduced units the radial distribution function and the intermediate scattering function are identical for state points that are isomorphic. The strain-rate dependent viscosity, which exhibits shear thinning, is also invariant along an isomorph. Our results extend the isomorph concept to the non-equilibrium situation of a shear flow, for which the phase diagram is three dimensional because the strain rate defines a third dimension.