Assessing the potential of zero charge in <i>ab initio</i> molecular dynamics simulations

Abstract

Accurate determination of the potential of zero free charge (PZFC) of an electrode from ab initio molecular dynamics (AIMD) simulations remains a longstanding challenge, largely due to ambiguities in computational setups and potential referencing at electrochemical interfaces. Here, we critically assess two widely used referencing strategies, the work-function (WF) and computational standard hydrogen electrode (cSHE) approaches, by combining a comprehensive analysis of literature data with new AIMD results. We demonstrate that both methods suffer from intrinsic limitations, arising from statistical uncertainty at the water/vacuum interface (WF) and from a strong dependence on setup-specific inner reference energies (cSHE). To overcome these shortcomings, we introduce a revised work-function approach (revWF) that unifies the strengths of both schemes while avoiding their principal weaknesses. The revWF method enables a more transferable and computationally efficient determination of the PZFC. Beyond these methodological considerations, we also reexamine and summarize the physical interpretation of the PZFC within the framework of an analysis originally suggested by Trasatti. Overall, this work provides practical guidelines for evaluating computational PZFCs and establishes revWF as a robust reference scheme for AIMD simulations of electrochemical interfaces.