Modeling the Photochromism of S-Doped Sodalites Using DFT, TD-DFT, and SAC-CI Methods

Structural Features, Chemical Diversity, and Physical Properties of Microporous Sodalite-Type Materials: A Review

This review contains data on a wide class of microporous materials with frameworks belonging to the sodalite topological type. Various methods for the synthesis of these materials, their structural and crystal chemical features, as well as physical and chemical properties are discussed. Specific properties of sodalite-related materials make it possible to consider they as thermally stable ionic conductors, catalysts and catalyst carriers, sorbents, ion exchangers for water purification, matrices for the immobilization of radionuclides and heavy metals, hydrogen and methane storage, and stabilization of chromophores and phosphors. It has been shown that the diversity of properties of sodalite-type materials is associated with the chemical diversity of their frameworks and extra-framework components, as well as with the high elasticity of the framework.

Reusable radiochromic hackmanite with gamma exposure memory

Radiochromic films are used as position-sensitive dose meters in e.g. medical physics and radiation processing. The currently available films like those based on lithium-10,12-pentacosdiynoate or leucomalachite green are either toxic or non-reusable, or both. There is thus a great need for a sustainable solution for radiochromic detection. In the present work, we present a suitable candidate: hackmanite with the general formula Na₈Al₆Si₆O₂₄(Cl,S)₂. This material is known as a natural intelligent material capable of changing color when exposed to ultraviolet radiation or X-rays. Here, we show for the first time that hackmanites are also radiochromic when exposed to alpha particles, beta particles (positrons) or gamma radiation. Combining experimental and computational data we elucidate the mechanism of gamma-induced radiochromism in hackmanites. We show that hackmanites can be used for gamma dose mapping in high dose applications as well as a memory material that has the one-of-a-kind ability to remember earlier gamma exposure. In addition to satisfying the requirements of sustainability, hackmanites are non-toxic and the films made of hackmanite are reusable thus showing great potential to replace the currently available radiochromic films.

The structural origin of the efficient photochromism in natural minerals

SignificanceNatural photochromic minerals have been reported by geologists for decades. However, the understanding of the photochromism mechanism has a key question still unanswered: What in their structure gives rise to the photochromism's reversibility? By combining experimental and computational methods specifically developed to investigate this photochromism, this work provides the answer to this fundamental question. The specific crystal structure of these minerals allows an unusual motion of the sodium atoms stabilizing the electronic states associated to the colored forms. With a complete understanding of the photochromism mechanism in hand, it is now possible to design new families of stable and tunable photochromic inorganic materials-based devices.

Unravelling the Origin of the Yellow-Orange Luminescence in Natural and Synthetic Scapolites

After decades of speculation without material proof, the yellow-orange luminescence of scapolite is definitely assigned to (S₂)^- activators trapped in [Na₄] square cages. Synthetic sulfur-doped scapolites confirm the implication of sulfur species in luminescence. Formally, the emission and excitation spectra of various polysulfide species were calculated. The excellent match between theory and experiments for (S₂)^- dimers provides definitive proof that it is the cause of the yellow-orange luminescence in scapolite.