Analysis of atomic displacement parameters and molecular motion in crystals

Abstract

First experiences in using the new computer-graphics program PEANUT for visualization and real-time manipulation of atomic anisotropic displacement parameters (ADP's) are illustrated by several examples. Kinematic and mixed kinematic-dynamic models of molecular motion in crystals are derived from observed ADP's in an iterative procedure for bis(<em>η</em>⁶-benzene)chromium, hexacarbonylchromium and boron nitrilotriacetate. The examples show that ADP's of high precision contain detailed information not only on rigid-body molecular motion and low-frequency intramolecular modes but also on intramolecular bending and stretching vibrations as well as on couplings between overall and intramolecular motion.