X-ray absorption coefficients of the Elements

Linear absorption coefficient
Linear absorption coefficient of materials defined by Eq (1).
        I=I₀ exp(-ux)                                                    (1)
M A for the database is a atomic absorption coefficient for a crystal. Using the atomic absorption coefficient for a crystal, we have
        u=z sum(M A)_i/(V 10^-24)                                (8)
where z is a chemical unit, V is the cell volume in Angstrom unit, and the summation is taken over the constituent elements in the chemical formula. For an exaple of tetragonal Tl2CaBa2Cu2O8 (z=2,V=435A³) at the wavelength =0.5A, the linear-absorption coefficient is calculated as u=196(cm-1).
  Furthermore, the linear-absorption coefficient, u, can be calculated from M/R as:
        u=d sum(p_i(M/R)_i)                                            (9)
where d is the density (g/cm3) of the material,pi is the fractional part(by weight) of the constituent elements of the compound, and  the summation is taken over all elements. The u value of the tungsten having the density of 19.24 g/cm3 is calculated at wavelength=0.5 A as u=~687 (cm-1).