How to clean CaF2 windows?
DO NOT USE ULTRASONIC CLEANING FOR CALCIUM FLUORIDE VIEWPORTS.
Always start by blowing off window first with clean, dry compressed air. ...
Always use a solvent-dampened swab to wipe clean a window, a dry swab can potentially scratch a window and. ...
Excess solvent should be flung off by a flip of the wrist.

What type of crystal structure is CaF2?
CaF₂ is Fluorite structured and crystallizes in the cubic Fm̅3m space group. Ca²⁺ is bonded in a body-centered cubic geometry to eight equivalent F¹⁻ atoms. All Ca-F bond lengths are 2.39 Å. F¹⁻ is bonded to four equivalent Ca²⁺ atoms to form a mixture of edge and corner-sharing FCa₄ tetrahedra.