TOPAS beq values

[Duncan, Jo]

Hello all.
 
This has no doubt been covered before and is probably in an obvious place but i 
just can't seem to find information on converting "beq" values in TOPAS to 
actual displacements (Angstroms).
 
Something to do with 4PIr^2 ?
 
Thanks in advance.
 
Happy refining!
 
Jo