Exploring PtSO4 and PdSO4 phases: an evolutionary algorithm based investigation

Abstract

Metal sulfate formation is one of the major challenges to the emission aftertreatment catalysts. Unlike the incredibly sulfation prone nature of Pd to form PdSO₄, no experimental evidence exists for PtSO₄ formation. Given the mystery of nonexistence of PtSO₄, we explore PtSO₄ using a combined approach of an evolutionary algorithm based search technique and quantum mechanical computations. Experimentally known PdSO₄ is considered for the comparison and validation of our results. We predict many possible low-energy phases of PtSO₄ and PdSO₄ at 0 K, which are further investigated in a wide range of temperature–pressure conditions. An entirely new low-energy (tetragonal P4₂/m) structure of PtSO₄ and PdSO₄ is predicted, which appears to be the most stable phase of PtSO₄ and a competing phase of the experimentally known monoclinic C2/c phase of PdSO₄. Phase stability at a finite temperature is further examined and verified by Gibbs free energy calculations of sulfates towards their possible decomposition products. Finally, temperature–pressure phase diagrams are computationally established for both PtSO₄ and PdSO₄.