EADP Instruction

EADP atomnames

The same isotropic or anisotropic displacement parameters are used for all the named atoms. The displacement parameters (and possibly free variable references) are taken from the named atom which precedes the others in the atom list, and the actual values, free variable references etc. given for the Uij of the other atoms are ignored. The atoms involved must either be all isotropic or all anisotropic. An atom should not appear in more than one EADP instruction. 'Opposite' fluorines of PF6 or disordered -CF3 groups are good candidates for EADP, e.g.

 EADP F11 F14
 EADP F12 F15
 EADP F13 F16
 C1 .......
 PART 1
 F11 ...... 21 ......
 F12 ...... 21 ......
 F13 ...... 21 ......
 PART 2
 F14 ...... -21 ......
 F15 ...... -21 ......
 F16 ...... -21 ......
 PART 0

EADP applies an (exact) CONSTRAINT. The SIMU instruction RESTRAINS the Uij components of neighboring atoms to be approximately equal with an appropriate (usually fairly large) esd.