Computational assessment of a proposed Na+/Ag+ ion-exchange route to Ag2MgSiO4, a predicted wurtzite-derived silver silicate
Year: 2026
Type: preprint
Abstract: Low-temperature ion exchange can provide a route to metastable inorganic compounds that are not favoured by equilibrium synthesis. We assess the proposed preparation of Ag2MgSiO4 from Na2MgSiO4 in molten AgNO3, using exchange energies, reported preparation controls and lattice-dynamical calculations. MLIP screening agrees in sign with the selected published DFT references, but the reaction set is linked by reciprocal reactions and thermodynamic cycles and is not an independent sample of synthesis outcomes. All screened Na-parent/AgNO3 exchanges pass the energy criterion; the Mg compound was carried forward by literatureguided judgement, not uniquely selected by that criterion. PBE gives exchange energies of about −58 kJ mol−1 per Ag and restricted O-balanced hull energies of 0.038–0.042 eV atom−1, comparable with reported silver silicates under the same calculation protocol. The exchange energies use an AgNO3 reference polymorph whose effect has not been tested with the same PBE settings. Corrected-code phonons support the Pna21 structure at the commensurate points and under the sampled tolerance, but stability beyond the chosen supercell and sampling is not established. A reanalysis of the archived outputs exposes limitations in the functional-property calculations: sparse path images do not establish DFT migration barriers, and incomplete exact-exchange sampling and single-reference gap shifting do not establish visible-light absorption. No synthesis or property measurement was performed. Ag2MgSiO4 remains a computational candidate for testing an exchange route; a failed experiment under one set of conditions would not by itself exclude the compound.
Source: ChemRxiv
Author: Chulmin Pyo
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220410798