@article {195, title = {Realistic molecular model of kerogen{\textquoteright}s nanostructure}, journal = {Nature Materials}, year = {2016}, month = {Feb-01-2016}, abstract = {

Despite kerogen\’s importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen\’s chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental\–simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen\’s nanostructure without considering the presence of clays and other minerals in shales. We probe the models\’ strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen\’s maturation, which manifests itself as an increase in the sp2/sp3 hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.

Kerogen in organic-rich shale formations.

Reconstruction of molecular models of kerogens.

Experimental validation of the molecular models.

Elastic properties of molecular models of kerogen.

}, issn = {1476-1122}, doi = {10.1038/nmat4541}, author = {Bousige, Colin and Ghimbeu, Cam{\'e}lia Matei and Vix-Guterl, Cathie and Pomerantz, Andrew E. and Suleimenova, Assiya and Vaughan, Gavin and Garbarino, Gaston and Feygenson, Mikhail and Wildgruber, Christoph and Franz-Josef Ulm and Roland Jean-Marc Pellenq and Benoit A. Coasne} } @article {142, title = {Optimized molecular reconstruction procedure combining hybrid reverse Monte Carlo and molecular dynamics}, journal = {The Journal of Chemical Physics}, volume = {142}, year = {2015}, month = {Mar-21-2015}, pages = {Article Number: 114112}, abstract = {

We report an efficient atom-scale reconstruction method that consists of combining the Hybrid Reverse Monte Carlo algorithm (HRMC) with Molecular Dynamics (MD) in the framework of a simulated annealing technique. In the spirit of the experimentally constrained molecular relaxation technique [Biswas et al., Phys. Rev. B 69, 195207 (2004)], this modified procedure offers a refined strategy in the field of reconstruction techniques, with special interest for heterogeneous and disordered solids such as amorphous porous materials. While the HRMC method generates physical structures, thanks to the use of energy penalties, the combination with MD makes the method at least one order of magnitude faster than HRMC simulations to obtain structures of similar quality. Furthermore, in order to ensure the transferability of this technique, we provide rational arguments to select the various input parameters such as the relative weight of the energy penalty with respect to the structure optimization. By applying the method to disordered porous carbons, we show that adsorption properties provide data to test the global texture of the reconstructed sample but are only weakly sensitive to the presence of defects. In contrast, the vibrational properties such as the phonon density of states are found to be very sensitive to the local structure of the sample.

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}, issn = {0021-9606}, doi = {10.1063/1.4914921}, author = {Bousige, Colin and Botan, Alexandru and Franz-Josef Ulm and Roland Jean-Marc Pellenq and Benoit A. Coasne} }