Exploring PtSO$_4$ and PdSO$_4$ phases: an evolutionary algorithm based investigation

TL;DR

This study uses evolutionary algorithms and quantum mechanics to predict stable phases of PtSO$_4$ and PdSO$_4$, revealing new structures and phase diagrams, and addressing the mystery of PtSO$_4$ formation.

Contribution

It introduces a combined computational approach to predict and analyze the phases of PtSO$_4$ and PdSO$_4$, including the discovery of a new stable structure for PtSO$_4$.

Findings

Predicted new low-energy tetragonal phase of PtSO$_4$ and PdSO$_4$.

Identified the most stable phase of PtSO$_4$ and a competing phase of PdSO$_4$.

Established temperature-pressure phase diagrams for both sulfates.

Abstract

Metal sulfate formation is one of the major challenges to the emissions aftertreatment catalysts. Unlike the incredibly sulfation prone nature of Pd to form PdSO$_4$, no experimental evidence exits for the PtSO$_4$ formation. Given the mystery of nonexistence of the PtSO$_4$, we explore the PtSO$_4$ using a combined approach of evolutionary algorithm based search technique and quantum mechanical computations. Experimentally known PdSO$_4$ is considered for the comparison and validation of our results. We predict many possible low-energy phases of the PtSO$_4$ and PdSO$_4$ at 0K, which are further investigated under wide range of temperature-pressure conditions. An entirely new low-energy (tetragonal $P4_2/m$) structure of the PtSO$_4$ and PdSO$_4$ is predicted, which appears to be the most stable phase of the PtSO$_4$ and a competing phase of the experimentally known monoclinic $C_2/c$ phase of PdSO$_4$. Phase stability at finite temperature is further examined and verified by free energy calculations of sulfates towards their possible decomposition products. Finally, temperature-pressure phase diagrams are computationally established for both PtSO$_4$ and PdSO$_4$.