Quantum chemical studies on peroxodisulfuric acid-sulfuric acid-water clusters

► Peroxodisulfuric acid (H2S2O8) forms stable clusters with sulfuric acid (H2SO4). ► Replacement of one H2SO4 by H2S2O8 in a pure H2SO4 cluster is thermodynamically favourable. ► However, the presence of H2S2O8 does not enhance the addition of further acid molecules to the clusters. ► Clustering significantly affects the characteristics of the SO-OS “oxygen bridge” bond.