Evidence of W- and M-type tetrad effects in acidic water systems

摘要

The tetrad effect consists of the subdivision of the general lanthanide contraction into four smooth curves (tetrads: La-Ce-Pr-Nd, Pm-Sm-Eu-Gd, Gd-Tb-Dy-Ho and Er-Tm-Yb-Lu), separated by three singular points which correspond to the increased stability at quarter, half, three-quarter, and complete filling of the 4f electron shell. The existence of this effect was first theoretically deduced and subsequently detected in experimental systems. However, the presence of the tetrad effect in natural systems has been widely criticized in spite of a wealth of evidence accumulated since 1979. Very few examples have been reported on the simultaneous presence of the conjugated tetrad effect (W- and M-type) in natural systems. Here we present evidence of this conjugated effect in an acidic water system associated with the precipitation of secondary amorphous phases.These solid phases showing the M-type tetrad effect while the waters develop an W-type.