Modeling In3+ and Sn2+ substitutions for Zn2+ in sphalerite via ab initio molecular dynamics calculations: key insights into critical metal mineralization

Computational framework for ab-initio calculations and molecular dynamics simulations of In 3+ and Sn 2+ substitutions for Zn 2+ in sphalerite. • The role of Sn in In-bearing sphalerite mineralization is critically examined. • Ab-initio calculations and simulations reveal In and Sn co-substitution mechanisms. • Substitution reactions exhibit a bimodal temperature dependence at 325 °C and 200 °C. • Findings enhance understanding of In enrichment in Sn-polymetallic deposits. Indium (In) is a strategically significant metal with an increasingly vital role in the global economy. It is a dispersed element with low crustal abundance, rarely forming independent deposits, and is primarily enriched in sphalerite through isomorphic substitution. In Sn-polymetallic deposits, In shows higher enrichment levels and is closely associated with Sn mineralization. Previous studies have suggested that Sn may occur as Sn 2+ in sphalerite, facilitating In incorporation via two key substitution mechanisms: In 3+ + Sn 2+ + Cu + → 3Zn 2+ and In 3+ + Sn 2+ + Ag + → 3Zn 2+ . However, the physicochemical conditions governing these mechanisms remain poorly constrained, limiting our understanding of In mineralization processes. This study employs ab initio molecular dynamics calculations to analyze the co-substitution of In and Sn for Zn within sphalerite in the presence of either Cu or Ag. We construct two doped systems, Zn 29 InCuSnS 32 and Zn 29 InAgSnS 32 , and investigate the effects of temperature and co-substituting metal ions on the enrichment process. Our findings indicate that the In-Sn-Cu substitution pathway, In 3+ + Sn 2+ + Cu + → 3Zn 2+ , is more favorable than the In-Sn-Ag pathway, In 3+ + Sn 2+ + Ag + → 3Zn 2+ . This process exhibits a pronounced high-temperature optimum at ∼ 325°C and a secondary minimum at a relatively low-temperature ∼ 200°C. This bimodal behavior suggests a general pattern of episodic, stage-wise, and complex coupled-decoupled enrichment of In in Sn polymetallic deposits, controlled by specific ore-forming conditions. These results provide valuable insights into the microscopic enrichment mechanisms of In in sphalerite, thereby advancing our understanding of In ore formation and guiding exploration.