Mutual Transformations of Polysulfide Chromophore Species in Sodalite‐Group minerals: A DFT Study on S6 Decomposition

It is known that various polysulfide species determine the color of sodalite‐group minerals (haüyne, lazurite, and slyudyankaite), and that heating induces their transformations and color change, but the mechanisms of the transitions are unknown. A prominent example is the decay of cyclic S 6 molecule. Using density‐functional simulations, we explore its main decay pathways into the most probable final reaction products (the pairs of radical anions S 3 ⋅ − +S 3 ⋅ − and S 2 ⋅ − +S 4 ⋅ − ). It was found that the most favorable reaction path involves initial capture of one electron by the S 6 molecule, which greatly facilitates its decay of S 6 and leads to the opening of the S 6 cycle, and subsequent decomposition of the thus formed chain radical anion, with a limiting energy barrier of ~0.4 eV. Neutral polysulfide molecules capture one electron with a significant energy reduction. The radical anions S n ⋅ − ( n =2−6) are the most stable ones among corresponding species with the same n values and different charges. The capture of the second electron by S 6 ⋅ − occurs with a huge energy barrier (~2 eV). The results of the DFT calculations are in agreement with experimental data on the products of thermal conversions of extra‐framework S‐bearing groups in sodalite‐group minerals.