Hi Jacob, Chek out Section 2 in the following paper: Echalier et al. (2004) Assessing crystallization droplets uding birefringence. Acta Cryst D60, 696-702.
It offers a very effective summary of the physical basis of crystal birefringence and reiterates the classification of crystal optics based on isotropic, uniaxial and biaxial systems. My understanding is that a favorable crystal orientation with respect to the direction of view is important for being able to observe appreciable birefringence from uniaxial and biaxial crystals. This can be especially tricky to get from biaxial crystals, i.e. crystals with orthorhombic or monoclinic or triclinic point-group symmetry, projecting their optically anisotropic axis in the plane of the view. Crystals with cubic symmetry are optically isotropic and are therefore not birefringent. Best wishes Savvas -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Jacob Keller Sent: Thursday, June 12, 2008 2:33 AM To: [email protected] Subject: [ccp4bb] birefringent spacegroups Dear Crystallographers, is there a list somewhere of spacegroups which can and cannot be birefringent? Upon what feature of the spacegroup does this depend? Jacob Keller ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program Dallos Laboratory F. Searle 1-240 2240 Campus Drive Evanston IL 60208 lab: 847.491.2438 cel: 773.608.9185 email: [EMAIL PROTECTED] *******************************************
