Extending Phase-Diagram Screening for Silicon Metallurgy: a Compact Pipeline Co-designed with a Ferroalloys Manufacturer

Silicon metallurgy relies on the reaction of silicon dioxide with elemental silicon in the presence of slag oxides that shift the balance between condensed and volatile phases of the Si-O system. In collaboration with a silicon-producing partner, we assembled a compact pipeline for screening slag compositions. First, it builds finite-temperature phase diagrams by combining Materials Project entries with the OQMD hull for oxides missing from MP (notably BO and other reduced Si-O compositions), applying a consistency correction to the OQMD side before merging. Second, it uses the Bartel finite-temperature approximation in pymatgen to extend $T=0$ K hulls up to $2000$ K, above Bartel's $\sim\!1800$ K calibration ceiling. Third, it complements DFT-based hulls with the CALPHAD method when TDB files are available. We cross-check the pipeline on the Si-O-B and Si-O-Al ternaries at $0$ K and $1450$ ºC against CALPHAD, and use it to score slag mixtures against process constraints (raw-material availability, cost of precursors, tolerance for volatile by-products). We discuss trade-offs against foundation-scale ML-only alternatives (MEGNet, ALIGNN, DPA-2), the practical limits imposed by the availability of TDB thermodynamic databases, and the fact that Bartel is applied here well above its calibration regime and on a molten (not crystalline) chemistry, so the extended hull is used as a bounding surface for locating the liquid slag pocket rather than as a phase-fraction predictor.