Atomistic Origin of Phase Stability in Oxygen-Functionalized MXene: A Comparative Study

Mishra, Avanish and Srivastava, Pooja and Carreras, Abel and Tanaka, Isao and Mizuseki, Hiroshi and Lee, Kwang-Ryeol and Singh, Abhishek K (2017) Atomistic Origin of Phase Stability in Oxygen-Functionalized MXene: A Comparative Study. In: JOURNAL OF PHYSICAL CHEMISTRY C, 121 (34). pp. 18947-18953.

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Abstract

Oxygen-functionalized MXene, M2CO2 (M = group III-V metals), are emergent formidable two-dimensional (2D) materials with a tantalizing possibility for device applications. Using first-principles calculations, we perform an intensive study, on the stability of fully O-functionalized (M2CO2) MXenes. Depending on the position of O atoms, the M2CO2 can a.) O atom occupies a site which is exactly on the top of the metal exist in two different structural phases. On one side of MXene, the atom from the opposite side. On the other side, the O atom can occupy either the site on the top of the metal atom of the opposite side (BB' phase) or on the top of the C atom (CB phase). We find that for M = Sc and Y the CB phase is stable, whereas for M = Ti, Zr, Hf, V, Nb, and Ta the stable phase is BB'. The electron localization function, the atom-projected density of states, the charge transfer, and the Bader charge analyses provide a rational explanation for the relative stability of these two phases and justify the ground state structure by giving information about the preferential site of adsorption for the O atoms. We also calculate the phonon dispersion relations for both phases of M2CO2. The BB'-Sc2CO2 and the CB-Ti2CO2 are found to `be dynamically unstable. Finally, we find that the instability of BB'-M2CO2 (M = Sc and Y) originates from the weakening of M-C interactions, which manifest as a phonon mode with imaginary frequency corresponding to the motion of C atom in the a-b plane. The insight into the stability of these competing structural phases of M2CO2 presented in this study is an important step in the direction of identifying the stable phases of these 2D materials.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICAL CHEMISTRY C
Additional Information:	Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	30 Sep 2017 09:20
Last Modified:	30 Sep 2017 09:20
URI:	http://eprints.iisc.ac.in/id/eprint/57941

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