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APPENDIX 10 - STANDARD ELEMENTAL RADII

The elemental radii (in Å) listed below are the standard values used to establish the crystal connectivity in the assemblage of CSD entries.

The distance D(A-B) between two atoms A and B is defined to be a bonding distance if:

R(A) + R(B) - TOL .LE. D(A-B) .LE. R(A) + R(B) + TOL

where:

R(A) is the elemental radius of atom A
R(B) is the elemental radius of atom B
TOL is a tolerance, normally 0.40Å.

In some entries the stored value of an elemental radius will differ from the standard value to encompass an unusually long or short bonding situation. Likewise the stored tolerance value may be different from 0.40Å.


  EL   R (Å)   EL      R (Å)   EL      R (Å)   EL      R (Å)
  Ac   1.88    Er      1.73    Na      0.97    Sb      1.46
  Ag   1.59    Eu      1.99    Nb      1.48    Sc      1.44
  Al   1.35    F       0.64    Nd      1.81    Se      1.22
  Am   1.51    Fe      1.34    Ni      1.50    Si      1.20
  As   1.21    Ga      1.22    Np      1.55    Sm      1.80
  Au   1.50    Gd      1.79    O       0.68    Sn      1.46
  B    0.83    Ge      1.17    Os      1.37    Sr      1.12
  Ba   1.34    H       0.23    P       1.05    Ta      1.43
  Be   0.35    Hf      1.57    Pa      1.61    Tb      1.76
  Bi   1.54    Hg      1.70    Pb      1.54    Tc      1.35
  Br   1.21    Ho      1.74    Pd      1.50    Te      1.47
  C    0.68    I       1.40    Pm      1.80    Th      1.79
  Ca   0.99    In      1.63    Po      1.68    Ti      1.47
  Cd   1.69    Ir      1.32    Pr      1.82    Tl      1.55
  Ce   1.83    K       1.33    Pt      1.50    Tm      1.72
  Cl   0.99    La      1.87    Pu      1.53    U       1.58
  Co   1.33    Li      0.68    Ra      1.90    V       1.33
  Cr   1.35    Lu      1.72    Rb      1.47    W       1.37
  Cs   1.67    Mg      1.10    Re      1.35    Y       1.78
  Cu   1.52    Mn      1.35    Rh      1.45    Yb      1.94
  D    0.23    Mo      1.47    Ru      1.40    Zn      1.45
  Dy   1.75    N       0.68    S       1.02    Zr      1.56
                                               X       0.00

The element symbol X is used ocasionally when a site is (equally) occupied by two elements. The radius assigned to X is then often the mean of the two elemental radii.


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