# Fixed and Refined Parameters

Fix and free parameters: occupancy, xyx, uiso

{occu, xyz, Uiso} [atoms]

Fixes the specified refinement parameter, i.e. these parameters will not be refined in subsequent refinement cycles.

• -occu: will fix the occupancy
• -xyz: will fix the xyz coordinates
• -Uiso: will fix the whole ADP

>>fix occu 0.5: will set and fix the occupancy of the current selection to 0.5 >>fix xyz: will fix the x, y and z co-ordinates of the currently selected atoms (i.e. not refine them).

## free

{occu, xyz, Uiso} [atoms]

The opposite of FIX - makes the specified parameters for the given atoms refineable. Freeing the occupancy is also available from the context menu.

## mode fixu

Fixes Uiso or ADP for subsequently clicked atoms.

## mode fixxyx

Fixes the coordinates for subsequently clicked atoms.

## mode occu

occupancy_to_set

Sets atom occupancy to the provided value for subsequently clicked atoms.