Unveiling the projection nature of solvation interactions yields a robust PMPA-MD method for efficient modeling of liquid-phase reactions: A case study on H2PtCl6 hydrolysis

While practically essential yet technically challenging, the lack of understanding of the nature of solvation interactions hinders the development of accurate and universal simulation methods for liquid-phase reactions. Here, we introduce an innovative concept of projecting intermolecular solvation interactions onto each atom/species, analogous to the way of quantifying covalent bonding interactions, and thereby developing a powerful tool of the Projective Multi-Point Averaging Molecular Dynamics (PMPA-MD), realizing consistent treatment of diverse solvation scenarios covering both liquid/solid interfaces and homogeneous solution reactions. Taking the multistep H2PtCl6 hydrolysis as an example, PMPA-MD demonstrates good accuracy with slight energy deviations <0.1 eV and reduces computational costs by approximately one order of magnitude, as compared with the benchmark constrained MD simulations. We show that the process is typically exothermic (except for the first hydrolysis step) and proceeds with surmountable reaction barriers following a Brønsted-Evans-Polanyi relationship. The substitution site is governed by the trans effect, while the substituent group (-OH or -H2O) exhibits piecewise pH dependence. Furthermore, elucidating the dynamic hydrolysis mechanism enables exploring the subsequent process of hydrolysate adsorption and reductive nucleation on the support surface, thereby shedding light on the morphology control of deposited Pt catalysts during experimental synthesis. This work advances both the concept and methodology for liquid-phase studies.