Oils with a lot of VI-improver usually exhibit this type of behaviour at low temperatures (ATF, multigrade engine oils). For non-Newtonian fluids this type of calculation is less accurate, especially at lower temperatures. If you know the viscosity of a Newtonian fluid at two different temperatures the equation can be solved and kinematic viscosities at other temperatures can be calculated. Reduce or increase the averaging parameter in the densities.The socalled Walther equation describes the temperature-viscosity relationship of Newtonian fluids. Run another simulated annealing simulation the data is too noisy, or the curves don’t intersect, we advise to try one of the following troubleshoots:
The subsets of points for the linear fits should be chosen such that a maximum R 2value is obtained. The intersection between these two lines marks the glass transition temperature. To calculate T g, carry out two linear fits through the data points as shown in the below figure. If the final and initial density are close, then the simulation can be considered converged and one can proceed with the calculation of T g. If the final density of the initial structure and the equilibrated structure differ significantly and the experimental density (if available) is far off, then the density is not converged and another simulated annealing run should be carried out. The graph will fall into one of two categories: Import the file into the plotting software of choice and plot the two columns against each other. The density profiles can be plotted with any graph plotting software, e.g. $AMSBIN/plams densities.py -v resultsdir=SimulatedAnnealing.results Calculation of the glass transition temperature ¶ In the command line, the script can be executed as follows Windows and Mac users should open a pre-configured command-line from the GUI Often the resulting structure is significantly lower in energy than the starting structure, though there is no guarantee it is the optimal one. The heating phase is followed by a cool down period in which the system is cooled back down to the initial temperature. During the annealing the temperature during an MD simulation is gradually increased, hoping that the system can overcome more and more energy barriers and explore the energy landscape effectively.
Simulated annealing is a simple optimization strategy intended to yield the global minimum energy structure on a complex and high dimensional potential energy surface. Large holes inside the polymer structure are an indicator for an inhomogeneous structure that will result in very noisy and hard to analyze results. In order to accurately simulate the temperature dependence of the density, we will have to make sure that the polymer structure is as homogeneous as possible. File → Import Coordinates Simulated annealing ¶
0 kommentar(er)
