> it could happen that the coordinates you got from the database > refer to a different origin...
Databases simply store the results of earlier determinations, for which the symmetry setting and coordinates should be coherent. It is not unknown for errors to occur, but commercial small structure databases ICSD and CSD are carefully checked, as are CIFs published in journals such as Acta Cryst. The easiest and most powerful check for a fundamental error in the structure description is to actually draw it on your computer - most mistakes, such as wrong origin, will be immediately apparent. Both ICSD and CSD allow you to draw structures. That's the first thing to do. BTW ICSD-Web http://icsdweb.fiz-karlsruhe.de/ will now draw anisotropic vibration amplitudes (also coming soon to Acta Cryst on-line). This is a good test for systematic errors in data and structure refinements, as is the calculation of bond-lengths and angles. Alan ______________________________________________ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE <[EMAIL PROTECTED]> +33.476.98.41.68 http://www.NeutronOptics.com/hewat ______________________________________________
