DELU s1 [0.01] s2 [0.01] atomnamesAll bonds in the connectivity list connecting atoms on the same DELU instruction are subject to a 'rigid bond' restraint, i.e. the components of the (anisotropic) displacement parameters in the direction of the bond are restrained to be equal within an effective standard deviation s1. The same type of restraint is applied to 1-3 distances as defined by the connectivity list (atoms 1, 2 and 3 must all be defined on the same DELU instruction). If s2 is omitted it is given the same value as s1. A zero value for s1 or s2 switches off the corresponding restraint. If no atoms are specified, all non-hydrogen atoms are assumed. DELU is ignored if (in the refinement cycle in question) one or both of the atoms concerned is isotropic; in this case a 'hard' restraint is inappropriate, but SIMU may be used in the usual way as a 'soft' restraint. DELU without atomnames applies to all non-hydrogen atoms (in the current residue); DELU_* without atoms applies to all non-hydrogen atoms in all residues. SFAC element names may also be referenced, preceded by the symbol '$'. The default values of s1 and s2 may be changed by means of a preceding DEFS instruction.
Back to FLAT
Back to Least-Squares Restraints
Back to Table of Contents