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# Diffraction Changes¶

## Powder Diffraction¶

### New features¶

• The ISIS powder diffraction scripts support the PaalmanPings correction method, calling PaalmanPingsMonteCarloAbsorption. To access it, set empty_can_subtraction_method: 'PaalmanPings' in the user config file. Also, there is new optional config settings (with their default values) paalman_pings_events_per_point: 1000.

• It is now possible to exclude specific banks from the total scattering merge banks for Polaris using -1 in the q_lims. For more details see Polaris.create_total_scattering_pdf.

• Added Total radial distribution function ($$G_k(r)$$) option to PDFFourierTransform v2.

• Added a switch to allow an absolute normalization to be performed by the ISIS powder diffraction scripts when running on the POLARIS instrument. As part of this the setting crystal_density has been removed from the SampleDetails class. The density of the material can now be set by supplying two of number_density, number_density_effective and packing_fraction.

• Users can now choose to run Polaris.create_total_scattering_pdf with either First order or Second order Placzek Corrections.

• Users can now choose to use either First order or Second order Placzek Corrections with TotScatCalculateSelfScattering.

### Bugfixes¶

• Changed the Fourier Filter applied during ISIS total scattering reduction so that $$g(r)=0$$ instead of $$g(r)-1=0$$.

• The error message raised when attempting to use the Polaris.create_total_scattering_pdf algorithm, if the focus has been run with do_van_normalisation=false, has been improved.

• Fixed an issue in the Powder Diffraction Reduction GUI where the GUI would crash when being launched the second time.

• Fixed deprecated syntax in LoadWAND that gives h5py warnings.

## Single Crystal Diffraction¶

### New features¶

• New TOPAZ IDF with updated calibration and current number of active banks.

• New integration algorithm IntegratePeaksSkew to integrate single-crystal Bragg peaks.

Release 6.5.0