Bulk Linear Diblock (linearDiblock.pre)

Keywords:

phase diagram, diblock, copolymer, morphologies, bulk behavior

Problem description

This simulation can be performed with a PSimBase license.

This example demonstrates the agreement between numerical self-consistent field theory calculations in PSim with the known theoretical result for a linear two-component copolymer system. One can choose (f, chiN) pairs and explore the phase morphologies of a bulk system of AB-diblock copolymer chains.

Input File Features

Files: linearDiblock.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)
  • dr (Grid cell size in the x-y-z-directions)
  • fA (Length fraction of ‘A’ block)
  • fB (Length fraction of ‘B’ block)
  • chiNAB (Flory \(\chi N\) parameter between the two chemically distinct blocks)
  • DS (Chain contour step size)
  • random_seed (Integer seed that sets the random number generator)
  • noise_strength (Strength factor for noise term in steepest descent relaxation)
  • lambda1 (Size of the first mixing factor for the steepest descent algorithm)

See the Linear Diblock Simulation Tutorial for more details.

Creating the run space

The Linear Diblock 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 “Linear Diblock” 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. 61.

../../../_images/linearDiblockSetupWin.png

Figure 61: Setup window for the Linear Diblock 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.
  • 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. 62.
../../../_images/linearDiblockRunWin.png

Figure 62: 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.
  • Go to the Scalar Data Variable in the Visualization 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. This is shown in the following figure Fig. 63
../../../_images/linearDiblockVizWin.png

Figure 63: Visualization of Linear Diblock examples as a color pseudocolor plot.

Further Experiments

Change the seed value. This will change the random initial condition of the chemical potential fields and will result in a different set of intermediate monomer density fields.

Change the overall size of the simulation by changing the number of cells in the NX, NY. The default for NZ is set to one for 2D simulations. Change NZ to explore full 3D morphologies.