MOF-5 (COD 1516287) has a cubic conventional cell with a=25.8247 angstrom. For a cubic cell, the interplanar spacing of the (h k l) lattice planes is d=a/sqrt(h^2+k^2+l^2). What is d for the (1 1 1) planes? Report the value in nanometers to six decimal places.

The Zn-only symmetry-expanded structure (S0004, 32 atoms) is attached for structural context; the calculation itself only needs the stated cell parameter a and the Miller indices (1,1,1). Do not use a value other than the stated a=25.8247 angstrom.