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Büchner C, Kubitza N, Malik AM, Jamboretz J, Riaz AA, Zhu Y, Schlueter C, McCartney MR, Smith DJ, Regoutz A, Rohrer J, Birkel CS. Chemical Conversions within the Mo-Ga-C System: Layered Solids with Variable Ga Content. Inorg Chem 2024; 63:7725-7734. [PMID: 38623051 DOI: 10.1021/acs.inorgchem.4c00107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Layered carbides are fascinating compounds due to their enormous structural and chemical diversity, as well as their potential to possess useful and tunable functional properties. Their preparation, however, is challenging and forces synthesis scientists to develop creative and innovative strategies to access high-quality materials. One unique compound among carbides is Mo2Ga2C. Its structure is related to the large and steadily growing family of 211 MAX phases that crystallize in a hexagonal structure (space group P63/mmc) with alternating layers of edge-sharing M6X octahedra and layers of the A-element. Mo2Ga2C also crystallizes in the same space group, with the difference that the A-element layer is occupied by two A-elements, here Ga, that sit right on top of each other (hence named "221" compound). Here, we propose that the Ga content in this compound is variable between 2:2, 2:1, and 2: ≤1 (and 2:0) Mo/Ga ratios. We demonstrate that one Ga layer can be selectively removed from Mo2Ga2C without jeopardizing the hexagonal P63/mmc structure. This is realized by chemical treatment of the 221 phase Mo2Ga2C with a Lewis acid, leading to the "conventional" 211 MAX phase Mo2GaC. Upon further reaction with CuCl2, more Ga is removed and replaced with Cu (instead of fully exfoliating into the Ga-free Mo2CTx MXene), leading to Mo2Ga1-xCuxC still crystallizing with space group P63/mmc, however, with a significantly larger c-lattice parameter. Furthermore, 211 Mo2GaC can be reacted with Ga to recover the initial 221 Mo2Ga2C. All three reaction pathways have not been reported previously and are supported by powder X-ray diffraction (PXRD), electron microscopy, X-ray spectroscopy, and density functional theory (DFT) calculations.
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Affiliation(s)
- Carina Büchner
- Department of Chemistry and Biochemistry, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Niels Kubitza
- Department of Chemistry and Biochemistry, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Ali M Malik
- Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - John Jamboretz
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
| | - Aysha A Riaz
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Yujiang Zhu
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | | | - Martha R McCartney
- Department of Physics, Arizona State University, Tempe, Arizona 85281, United States
| | - David J Smith
- Department of Physics, Arizona State University, Tempe, Arizona 85281, United States
| | - Anna Regoutz
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Jochen Rohrer
- Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Christina S Birkel
- Department of Chemistry and Biochemistry, Technische Universität Darmstadt, 64287 Darmstadt, Germany
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85281, United States
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Kubitza N, Büchner C, Sinclair J, Snyder RM, Birkel CS. Extending the Chemistry of Layered Solids and Nanosheets: Chemistry and Structure of MAX Phases, MAB Phases and MXenes. Chempluschem 2023; 88:e202300214. [PMID: 37500596 DOI: 10.1002/cplu.202300214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 07/29/2023]
Abstract
MAX phases are layered solids with unique properties combining characteristics of ceramics and metals. MXenes are their two-dimensional siblings that can be synthesized as van der Waals-stacked and multi-/single-layer nanosheets, which possess chemical and physical properties that make them interesting for a plethora of applications. Both families of materials are highly versatile in terms of their chemical composition and theoretical studies suggest that many more members are stable and can be synthesized. This is very intriguing because new combinations of elements, and potentially new structures, can lead to further (tunable) properties. In this review, we focus on the synthesis science (including non-conventional approaches) and structure of members less investigated, namely compounds with more exotic M-, A-, and X-elements, for example nitrides and (carbo)nitrides, and the related family of MAB phases.
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Affiliation(s)
- Niels Kubitza
- Department of Chemistry and Biochemistry, Technische Universitaet Darmstadt, 64287, Darmstadt, Germany
| | - Carina Büchner
- Department of Chemistry and Biochemistry, Technische Universitaet Darmstadt, 64287, Darmstadt, Germany
| | - Jordan Sinclair
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA
| | - Rose M Snyder
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA
| | - Christina S Birkel
- Department of Chemistry and Biochemistry, Technische Universitaet Darmstadt, 64287, Darmstadt, Germany
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA
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Dau MT, Al Khalfioui M, Michon A, Reserbat-Plantey A, Vézian S, Boucaud P. Descriptor engineering in machine learning regression of electronic structure properties for 2D materials. Sci Rep 2023; 13:5426. [PMID: 37012307 PMCID: PMC10070413 DOI: 10.1038/s41598-023-31928-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 03/20/2023] [Indexed: 04/05/2023] Open
Abstract
We build new material descriptors to predict the band gap and the work function of 2D materials by tree-based machine-learning models. The descriptor's construction is based on vectorizing property matrices and on empirical property function, leading to mixing features that require low-resource computations. Combined with database-based features, the mixing features significantly improve the training and prediction of the models. We find R[Formula: see text] greater than 0.9 and mean absolute errors (MAE) smaller than 0.23 eV both for the training and prediction. The highest R[Formula: see text] of 0.95, 0.98 and the smallest MAE of 0.16 eV and 0.10 eV were obtained by using extreme gradient boosting for the bandgap and work-function predictions, respectively. These metrics were greatly improved as compared to those of database features-based predictions. We also find that the hybrid features slightly reduce the overfitting despite a small scale of the dataset. The relevance of the descriptor-based method was assessed by predicting and comparing the electronic properties of several 2D materials belonging to new classes (oxides, nitrides, carbides) with those of conventional computations. Our work provides a guideline to efficiently engineer descriptors by using vectorized property matrices and hybrid features for predicting 2D materials properties via ensemble models.
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Affiliation(s)
- Minh Tuan Dau
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Grégory, 06560, Valbonne, France.
| | - Mohamed Al Khalfioui
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Grégory, 06560, Valbonne, France
| | - Adrien Michon
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Grégory, 06560, Valbonne, France
| | | | - Stéphane Vézian
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Grégory, 06560, Valbonne, France
| | - Philippe Boucaud
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Grégory, 06560, Valbonne, France
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Wong ZM, Tan TL, Yang SW, Xu GQ. Optimizing special quasirandom structure (SQS) models for accurate functional property prediction in disordered 2D alloys. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:485402. [PMID: 30406769 DOI: 10.1088/1361-648x/aae764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
2D materials such as MXenes have garnered attention in a wide field of applications ranging from energy to environment to medical. Properties of 2D materials can be tailored via alloying and in some cases, solid-solutions (disordered alloys) are formed. To predict the disordered alloy properties via first-principles, the model structure needs to imitate the random arrangements of alloyants and yet remains computationally tractable. Using density functional theory and the cluster expansion method, we investigate the accuracy of using of special quasirandom structures (SQSs) for predicting disordered 2D alloy properties, evaluating the effect of SQS supercell size on the prediction quality of formation energies, elastic properties, and structural parameters. We illustrate the findings with 5 different disordered binary [Formula: see text] MXene alloy systems (where M = Ti and M' = Zr, Hf, V, Nb, or Ta), demonstrating that SQSs around 6-8 times the primitive cell (N = 6-8) are sufficient to attain convergence in the property predictions versus supercell size. For formation energies, SQSs with N > 4 are found to reproduce the formation energies of the fully disordered phase within ~2.5 meV. For the simulation of the experimentally-synthesized TiNbCO2, we find convergence in structural parameters and elastic tensors at N ~ 6. We traced the convergence of the predictions to the convergence in the band structure-related properties via analysis of the electronic densities-of-states and the projected crystal overlap Hamilton population. Our findings suggest that modest sized SQSs would reproduce the properties of disordered MXene alloys. The results should help guide the investigations of structure-property relationships in other disordered 2D materials as well.
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Affiliation(s)
- Zicong Marvin Wong
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore. Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore
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