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Lattice Strains Optimizations

Test corrections and fit of lattice strain equation

You should first test

• the corrections you chose
• the validity of the lattice strain equation.

Once again, the lattice strain equation used in Polydefix is derived using an elastic theory and might not match the data.

To check your fits, use the Stress and strain -> Test fit quality menu item. You will be able to choose

• which diffraction image you want to look at (use the shift key to select multiple images)
• which diffraction line to plot.

Test of the lattice strain equation

In the plot window, black stars are position of diffraction lines deduced from the x-ray data and the red curve are fits of the lattice strain equations.

When the stress is low, fits might look a bit disturbing because changes in d-spacing with orientation are small. It is better to select several images and different points in the compression cycle and check that the evolution of the lattice strains with deformation is OK.

Lattice strains

Evolution of the lattice strain parameters Q with image number can be plotted, exported to text files, and listed in the Stress and strain -> Lattice strains menu item.

As for other functions, plots can be saved as images for further use.

Lattice strain parameter Q vs. image number