DS10 - Défi des autres savoirs

Tenebrescent minerals by in silico Modelling – TeneMod

Submission summary

Photochromic compounds are the base of numerous potential high-tech devices including adaptive glasses, photo-switches, optical memories etc. Up to now, this research field has been dominated by organic materials because of the large versatility offered by organic synthesis to design and tune molecules. The lack of adaptability of inorganic photochromic materials is the main brake on their development although they possess some interesting properties such as good working condition stability. The lack of adaptability of inorganic materials could be solved by natural minerals of the sodalite family. The natural photochromism of these minerals has been known from geologists (who call this phenomenon tenebrescence) for around 50 years but has been started to be investigated seriously only recently. Up to now, the only assessed mechanism of the photochromism was a photo-induced electron transfer from a sulfur-based impurity toward a chlorine vacancy creating a F-center, giving a colour to the system. But no atomistic model of the system was developed to clearly confirm this mechanism. The TeneMod project stands there. We want to develop a methodology based on quantum chemistry to uncover the elementary steps of photochromism mechanism in sodalite leading to an accurate simulation of the phenomenon and of the final colour of the system. With this methodology we will perform a large benchmark of colour simulation and activation energy of all photochromic (tenebrescent) natural minerals of the sodalite family known in geology and on potential artificial sodalites to determine the adaptability of these minerals for further investigations.
The TeneMod project is organized in five tasks. The Task 1 is dedicated to the development of the methodology on the most simple photochromic sodalite. This approach involves geometries determined by DFT in periodic boundary conditions and sophisticated excited state simulations (TD-DFT, SAC-CI…) computed on clusters extracted from the PBC geometries surrounded by an environment simulating the Madelung potential of the crystal. The methodology is then tested on natural tugtupite and scapolite tenebrescent mineral in Task 2 with the objectives first to improve the methodology if necessary then to understand the influence of the crystal structure on the photochromism. The Task 3 will focus on artificial sodalite with the simulation of their photochromic properties, by changing the chemical nature of the constituting atoms and the dopants, to demonstrate the adaptability of these minerals for the practical applications. In the Task 4, we will move toward a realistic colour simulation including the light scattering of the powder nature of the material. The final Task has the objective to prove that the methodology developed by TeneMod can be used for other spectroscopic modelling, like the difficult simulation of alexandrite and cordierite polychromism.
From a practical point of view, a funding of ~160k€ is asked for this project. A large part of this funding will be used for a PhD fellowship. Beyond the PhD student and myself, TeneMod will involve one of the world expert in the synthesis of artificial sodalite, Pr. Mika Lastusaari, and some colleagues of my host-laboratory. The TeneMod project corresponds to a new field of research in my host laboratory. This project will be the first large quantum chemical investigation of this family of material, bringing my team as the leader on the modelling of these minerals with the objective to offer to the community both an atomistic point of view that is missing to inorganic photochromism research field and the proof that an adaptable, stable and cheap mineral can be developed for photochromic devices.

Project coordinator

Monsieur Tangui Le Bahers (Laboratoire de chimie / ENS Lyon)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LCH / ENS de Lyon Laboratoire de chimie / ENS Lyon

Help of the ANR 154,272 euros
Beginning and duration of the scientific project: September 2017 - 48 Months

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