I have crystal structure of a compound (a salt) which is a triclinic cell. Now I want to determine the radius of cation and anion. How can I do it please explain.
Many thanks in advance.
Looking forward...
Sandipan
You cannot calculate the radii of atoms from a given crystal structure.
You can calculate the interatomic distance between any pair of atoms. By comparing the interatomic distances to different neighbors you might be able to deduce a bit of an estimate of atomic radii. Keep in mind that atomic radii are rather ill defined parameters.
In any crystal system the proper way to calculate the length of a real space vector is:
d^2 = (x, y, z) * (G) * (x, y, z)^T
with
d^2 the length squared
(x, y, z) a row vector of the fractional coordinates of the vector
G the metric tensor with elements G_ij = a_*a_j the scalar products of the three base vectors = |a_i| * |a_j|*cos(angle(a_i,a_j))
(x,y,z)^T the column vector of the fractional coordinates.
For your calculation, (x, y, z) is, trivially, the difference vector between the two atom coordinates.
You should look this up in any standard introductory textbook to crystallography like Giacovazzo et al "Fundamentals of crystallography"; D.E. Sand " Vectors and tensors in crystallography"
Dear R. B. Neder ,
Many thanks for your answer. But I am wondering that can it be done by any software like Mercury or others?
Thank you
Of course, all programs that are used to display crystal structures (like Jmol, Vest, Atoms, Diamond etc etc) will have a tool to measure the distance between a pair of atoms. Just look at the manual of the program you use.
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