Hi, I would like to survey the group for causes and potential solutions to unstable refinement (the steady and upward drift of R and Rfree in each cycle of refinement). I am currently aware of the following potential causes: twinning (meohedral, pseduomerohedral, or epitaxial), anisotropy, pseudosymmetry, the lack of appropriately tight geometric constraints, and extraordinarily high b-factors. If anyone has run into any other causes of unstable refinement, I would like to hear about them.
Thanks, John Bruning
