Journal of Applied Crystallography

Volume 34, Part 4 (August 2001)

research papers

J. Appl. Cryst. (2001). 34, 480-483 [ doi:10.1107/S0021889801008470 ]

On planarity and similarity restraints

E. Blanc and W. Paciorek

Abstract: Planarity and similarity restraints are described using a unified framework for the computation layout. In both cases, the gradient and Hessian of the restraint residual with respect to atomic coordinates are derived. All computed quantities (residual, gradient, Hessian, normal and distance to the plane for planarity restraints, rotation and translation in the case of similarity) can be obtained directly, without iterative procedure.

Keywords: planarity and similarity restraints; structure refinement.