Index

Core dictionary version 3.0.14

_atom_site.tensor_beta

Definition:

   
     The symmetric anisotropic atomic displacement tensor beta[I,J]
     appears in a structure factor expression as:
 
     t = exp -[ beta11 h h + ............ 2 beta23 k l ]
 
     It is related to the adp matrices U(IJ) and B(IJ) as follows:
 
     t = exp -2pi**2 ( U11    h h a* a* + ...... 2 U23    k l b* c* )
     t = exp - 0.25  ( B11    h h a* a* + ...... 2 B23    k l b* c* )

Type: Real

Values appear in Matrix context.

Dimension: [3,3]

Evaluation method:

     With  a  as  atom_site
 
     label = a.label
 
     If      (a.adp_type == 'Uani')  {
         Loop b as atom_site_aniso     {
           If(label == b.label)           {
 
               UIJ = b.matrix_U
               Break
     } } }
 
     Else If (a.adp_type == 'Bani')  {
         Loop b as atom_site_aniso     {
           If(label == b.label)           {
 
              UIJ = b.matrix_B / (8 * Pi**2)
              Break
     } } }
 
     Else                                    {
         If (a.adp_type == 'Uiso')  U  =  a.U_iso_or_equiv
         Else                       U  =  a.B_iso_or_equiv / (8 * Pi**2)
 
             UIJ = U * _cell.convert_Uiso_to_Uij
     }
 
              CUB = _cell.convert_Uij_to_betaij
 
        _atom_site.tensor_beta =  CUB * UIJ * CUB

Category:
atom_site