Is it Ever Acceptable to SQUEEZE Charge Balance?

TL;DR

The paper discusses when it is acceptable to use charge balance squeezing in crystallography when solvent molecules or counter-ions are too disordered to model accurately.

Contribution

The paper explores the conditions under which squeezing charge balance is justifiable when counter-ions are disordered.

Findings

SQUEEZE routines are typically used for disordered solvent molecules.

The paper questions the use of squeezing when counter-ions are disordered.

Additional characterization may justify squeezing charge balance.

Abstract

When the void spaces of a structure contain highly disordered solvent molecules that cannot be adequately modeled, the SQUEEZE routine of PLATON or Solvent Mask in Olex2 are often used as a last resort to account for the electron density in the void spaces. But, what to do when it is not solvent molecules that are disordered? What if the counter-ions for a charged target molecule are so disordered that they cannot be definitively identified in the difference map? Is there a point at which there is enough additional characterization of a compound that squeezing charge balance could be considered acceptable?