Cation Exchange in Selenide Nanocrystals

Cation exchange is one of the most useful tricks in colloidal nanocrystal chemistry: because the Se²⁻ anion sublattice of a II–VI or IV–VI selenide is far less mobile than its cations, a CdSe nanocrystal can be converted into PbSe or Ag₂Se — a completely different semiconductor with a completely different bandgap — while keeping the exact same size and shape. This simulator renders the fixed anion lattice and the cation sites of a real nanocrystal in 3D, drives a shrinking-core reaction front inward at an Arrhenius-activated rate you control with temperature and reagent choice, and tracks the live conversion fraction, front position and Brus-model effective bandgap as the particle transforms from wide-gap CdSe into a narrow-gap product.