Universal 'bond valence versus bond length' correlation curve for manganese-oxygen bonds

The oxidation-state independent 'bond valence (s) versus bond length (r)' correlation curve for manganese-oxygen bonds has been closely approximated using the modified two-parameter Tromel s = f(r) function [Tromel (1983). Acta Cryst. B39, 664-669], s = [(r(0) - l)/(r - l)](2), where r(0) = 1.763 (2) angstrom and l = 1.148 (9) angstrom. The r(0) and l refinable parameters of the above function can be regarded as the alternative bond-valence parameters intended for use in the modern bond-valence model [Brown (2009). Chem. Rev. 109, 6858-6919] in cases where the traditional bond-valence parameters (r(0); n) and (r(0); b) fail.