Unlocking Phase Diagrams for Molybdenum and Tungsten Nanoclusters and Prediction of their Formation Constants

Abstract

Understanding and controlling aqueous speciation of metal oxides are key for the discovery and development of novel materials, and challenge both experimental and computational approaches. Here we present a computational method, called POMSimulator, which is able to predict speciation phase diagrams (Conc. vs pH) for multispecies chemical equilibria in solution, and which we apply to molybdenum and tungsten isopolyoxoanions (IPAs). Starting from the MO4 monomers, and considering dimers, trimers, and larger species, the chemical reaction networks involved in the formation of [H32Mo36O128]8– and [W12O42]12– are sampled in an automatic manner. This information is used for setting up ∼105 speciation models, and from there, we generate the speciation phase diagrams, which show an insightful picture of the behavior of IPAs in aqueous solution. Furthermore, we predict the values of 107 formation constants for a diversity of molybdenum and tungsten molecular oxides. Among these species, we could include several pentagonal-shaped species and very reactive tungsten intermediates as well. Last but not least, the calibration employed for correcting the density functional theory (DFT) Gibbs energies is remarkably similar for both metals, which suggests that a general rule might exist for correcting computed free energies for other metals.

Computational Prediction of Speciation Diagrams and Nucleation Mechanisms: Molecular Vanadium, Niobium, and Tantalum Oxide Nanoclusters in Solution

“…Following this trend, we have recently reported the development of a new method, called POMSimulator, that automatically generates the CRN for a set of metal-oxo-clusters from raw quantum chemical results and predicts both speciation diagrams and the corresponding reaction mechanism . Hitherto, we have applied this method to polyoxomolybdates and -tungstanates with excellent results …”

“…48 Hitherto, we have applied this method to polyoxomolybdates and -tungstanates with excellent results. 49 In this work, we exploit the capabilities of POMSimulator to predict the aqueous speciation and nucleation mechanisms of group V polyoxometalates. We have considered 122 metal-oxoclusters in total, including classical structures such as Lindqvist {M 6 } and decametalate {M 10 }.…”

Computational Prediction of Speciation Diagrams and Nucleation Mechanisms: Molecular Vanadium, Niobium and Tantalum Oxide Nanoclusters in Solution

“…This is so because theoretical constants are overestimated with respect to the experimental values. 49,53 For molybdenum and tungsten oxides, we have recently found a strong linear dependence between DFT and empirical formation constants, thus granting the application of a systematic linear scaling. 54 Therefore, the first milestone for predicting Group V aqueous speciation depended on the accuracy of the linear scaling.…”

“…48 Hitherto, we have applied this method to polyoxomolybdates and -tungstanates with excellent results. 49 In this work, we exploit the capabilities of POMSimulator to predict the aqueous speciation and nucleation mechanisms of Group V polyoxometalates. We have considered 122 metal-oxo clusters in total, including classical structures such as Lindqvist {M6} and decametalate {M 10 }.…”

Composition-driven archetype dynamics in polyoxovanadates

“…First, concentrated solutions of V 6 As 8 led to deposition of a crystalline solid containing To resolve the structure of [V 10 As 12 O 40 ] 4À using computational brute force would require the simulation of thousands of different POV scenarios that surpasses any current achievement in the eld. 43,44 However, empirical intelligence and systems thinking combined with care for retention of local coordination environments (i.e. concept synthesis) can provide a signicantly constrained direction in which suitable models can be discovered (see Fig.…”