Zone Annealing (zoneAnneal.pre)

Keywords:

random-phase approximation, phase transition

Problem description

This simulation can be performed with a PSimBase license.

The steepest-descent alogorithm can lead to simulations results that represent metastable or weakly unstable states. Many of these non-equilibrium morphologies are due to the presence of topological defects. In a lamellar (LAM) phase these defects can manifest as layer dislocations. This example shows how to implement a zone-annealing technique that can aid in rapidly removing these defects.

Input File Features

Files: zoneAnneal.pre.

The variables in the Setup tab are

  • NX (Number of cells in the x-dir)
  • NY (Number of cells in the y-dir)
  • NZ (Number of cells in the z-dir)
  • zoneVelocity (Velocity of center of zone)
  • sizeZone (Number of grid cells across width of moving zone)
  • edgeWidth (Controls width of zone edges)
  • sweepsMax (Number of sweeps before zone is turned off)

The following block demonstrates the STFunc ‘switchMovTanhSlab’ that the Flory interaction block uses to implement the zone annealing technique

<Interaction StyrEthy>

  kind = flory
  scfields = [totStyrDens totEthyDens]

  <STFunc chirzoneY>
    kind = switchMovTanhSlab
    widthParam = edgeWidth
    zoneSize = sizeZone
    chiNmax = 8.0
    chiNmin = 20.0
    zoneBuffers = [ xzoneBuffer yzoneBuffer ]
    expression = -80.0 + zoneVelocity*t
    maxSweeps = sweepsMax
  </STFunc>

</Interaction>

Creating the run space

The Zone Annealing example is accessed from within PSimComposer by the following actions:

  • Select the New from Template menu item in the File menu.
  • In the resulting New from Template window, select PSimBase and then press the arrow button to the left.
  • Select “Zone Annealing” and press the Choose button.
  • In the resulting dialog, press the Save button to create a copy of this example in your run area.

The basic variables of this problem should now be settable in text boxes in the right pane of the “Setup” window, as shown in Fig. 78.

../../../_images/zoneAnnealSetupWin.png

Figure 78: Setup window for the Zone Annealing example.

Running the simulation

After performing the above actions, continue as follows:

  • Press the Save And Setup button in the upper right corner.
  • Proceed to the run window as instructed by pressing the Run button in the left column of buttons.
  • Note: because the initial random state depends on the number of processors, the final simulation state can depend on the number of processors chosen if running in parallel. The results in this example are produced by running on two processors. The parallel run options can be accessed by going to the ‘MPI’ tab on the left side of the Run button window.
  • To run the file, click on the Run button in the upper right corner. of the window. You will see the output of the run in the right pane. The run has completed when you see the output, “Engine completed successfully.” This is shown in Fig. 79.
../../../_images/zoneAnnealRunWin.png

Figure 79: The Run window at the end of execution.

Visualizing the results

After performing the above actions, continue as follows:

  • Proceed to the Visualize window as instructed by pressing the Visualize button in the left column of buttons.
  • Press the “Open” button to begin visualizing.
  • Go to the Scalar Data Variable in the CONTROLS panel on the left and press the arrow to the left
  • Check one of the MonomerDensity boxes (try the totEthyDens database) This selects all of the datafiles for this physical field ‘totEthyDens’. This first *h5 file will be shown first.
  • Move the Dump slider at the bottom of the window to the last position to see the final simulation state.
../../../_images/zoneAnnealVizWin.png

Figure 80: Visualization of Zone Anneal as a color contour plot.

Further Experiments

Change the overall size of the system (NX, NY, and/or NZ) to see the zone annealing effects on a simulation with more topological defects.

Change the size and speed of the annealing zone to see effect on long-range ordering.