CrysAlis^Pro Tip

Forcing a User-defined Lattice for Processing

What is the issue?

CrysAlis^Pro may occasionally change the lattice upon processing and select the wrong one. This may occur even if the correct lattice was selected upon indexing. Let us hypothesize that this is taking place for a monoclinic unit cell with a beta angle close to 90° and CrysAlis^Pro has mistakenly set the lattice to orthorhombic.

How to select the correct monoclinic unit cell?

First and foremost, one must reindex the diffraction pattern in the correct monoclinic unit cell.

1) In Lattice Wizard, run Peak hunting and Unit cell finding as usual.

2) Click on the blue button Lattice transformation:

Figure 1. Lattice transformation button in Lattice Wizard

3) Select the desired unit cell from the list displayed, as shown below, and click OK:

Figure 2. Transformed Cell List

How to force a lattice type onto CrysAlis^Pro?

One must now set CrysAlis^Pro so it will not change the lattice type on its own.

4) Go back to Lattice transformation but this time, click on the small, blue arrow and select Lattice transformation with user matrix:

Figure 3. Lattice transformation with user matrix

5) The line of 9 numbers displayed is in fact a 3 x 3 matrix that one can use to alter the unit cell dimensions. In this case, the dimensions are already correct from the previous indexing. So, just select Apply:

Figure 4. Unit Cell Dimension Transformation Matrix

6) The primitive cell is displayed. Check the User cell box and select the desired lattice type and body centering option. Then, click OK:

Figure 5. Check the User cell box and select the desired lattice type and body centering option

7) The correct lattice is now displayed, and it is preceded by the code UmP, which signifies user-monoclinic-primitive:

Figure 6. The correct lattice is now displayed

8. Close Lattice Wizard and proceed with data processing. The user-defined cell and lattice will be kept by CrysAlis^Pro throughout data integration, scaling and space group search.