Phonon-mediated stabilization and softening of 2D transition metal carbides: case studies of Ti2CO2 and Mo2CO2

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	Phonon-mediated stabilization and softening of 2D transition metal carbides: case studies of Ti2CO2 and Mo2CO2
	Zhang, Ruifeng; Francisco, Joseph S.; Du, Shiyu; Si, Chen; Germann, Timothy C.; Legut, Dominik; Fu, Zhongheng
刊名	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
	2018
卷号	20 期号:21 页码:14608-14618
关键词	2-dimensional Molybdenum Carbide Ideal Strength Thermodynamic Stability Energy-storage Mxenes Instability Nitrides Capacity Graphene Tension
英文摘要	Two-dimensional transition metal carbides (MXenes) exhibit excellent thermodynamic stability, mechanical strength and flexibility, which make them promising candidates in flexible devices and reinforcements in nanocomposites. However, the dynamic stability may intrinsically determine the preferred adsorption sites of functional groups in MXenes and lead to premature failure under finite strain before approaching the elastic limits. It is found interestingly that different adsorption sites of the functional groups correspond to the different phonon stabilities and adsorption energies of MXenes, which can be attributed to different hybridization characteristics between the metal-d and O-p(z) states and delocalized electron behaviors around the metal atoms. Although both Ti2CO2 and Mo2CO2 possess high ideal strengths and superior flexibility, the premature phonon instabilities appear unexpectedly in distinct manners before approaching their elastic limits. An in-depth exploration of the soft modes and deformed electronic structures reveals that a continuously decreasing gap-opening at the point in Ti2CO2 increases after in-plane phonon instability due to the pseudo Jahn-Teller effect, differing from the out-of-plane phonon instability and semiconductor-metal transition under biaxial tension observed in MoS2. Although Mo2CO2 shows similar failure modes to graphene under uniaxial/biaxial tensions, the band crossings around the Fermi level are found to be responsible for its metallic character and elastic/phonon instabilities by modifying the elastic energy or electronic band energy, different from the gap opening appearing in graphene. Our results shed light onto the profound effect of the phonon instability on the preferable structure and strengths of MXenes, providing theoretical guidance on designing flexible MXene devices, raising a great challenge to the conventional strengthening theory by simply counting bonds.
学科主题	Materials Science ; Metallurgy & Metallurgical Engineering
语种	英语
公开日期	2018-12-04
内容类型	期刊论文
源URL	[http://ir.nimte.ac.cn/handle/174433/17411]
专题	2018专题
推荐引用方式 GB/T 7714	Zhang, Ruifeng,Francisco, Joseph S.,Du, Shiyu,et al. Phonon-mediated stabilization and softening of 2D transition metal carbides: case studies of Ti2CO2 and Mo2CO2[J]. PHYSICAL CHEMISTRY CHEMICAL PHYSICS,2018,20(21):14608-14618.
APA	Zhang, Ruifeng.,Francisco, Joseph S..,Du, Shiyu.,Si, Chen.,Germann, Timothy C..,...&Fu, Zhongheng.(2018).Phonon-mediated stabilization and softening of 2D transition metal carbides: case studies of Ti2CO2 and Mo2CO2.PHYSICAL CHEMISTRY CHEMICAL PHYSICS,20(21),14608-14618.
MLA	Zhang, Ruifeng,et al."Phonon-mediated stabilization and softening of 2D transition metal carbides: case studies of Ti2CO2 and Mo2CO2".PHYSICAL CHEMISTRY CHEMICAL PHYSICS 20.21(2018):14608-14618.