Electronic and elastic correlations in AlB₂-type two-dimensional hexagonal MBenes

Abstract

With the advent of MXenes as two-dimensional (2D) materials beyond graphene, non carbonic 2D materials analogically referred as MBenes have significantly attracted researchers’ attention. Such 2D MBenes remains largely unexplored. Here, we systematically investigate electronic and elastic properties of 2D transition metal (TM) based AlB2-type hexagonal MBenes consisting of a honeycomb networked graphene like boron layer embedded with diverse TM atoms at center. First we determine the thermodynamic, dynamic, thermal, and mechanical stability of MBenes, considering a wide range of 3d, 4d, and 5d TM elements. Electronic and elastic calculations are performed for stable MBenes in order to parameterize and investigate the interdependence of properties. Elastic calculations predicts the brittle-ductile nature and bond character of MBenes while unraveling the in-plane auxetic behavior. Our electronic calculations predict the metallic band nature for 2D VB2, NbB2, TaB2, and WB2 along with previously reported dirac points in 2D TiB2, FeB2, ZrB2, and HfB2. The elastic and electronic calculations clearly indicates the non-directional metallic bonds and intrinsically ductile nature of 2D-FeB2 distinct from other MBenes. Subsequently we performed a covariance analysis to assess the correlation amongst the observables of interest and further establish the interdependence of the properties. Our calculations for elastic correlations also suggests that mechanical brittle-ductile nature and auxetic behavior of MBenes can be tuned by strain engineering of the elastic constants. Our results further suggests that strong correlations between Poisson ratio and d state electrons can be utilized to tune the auxetic behavior by careful doping of the materials. Our work demonstrates the weak elastic-electronic correlations, suggesting that the strain engineering can be utilized for the tailored behavior of MBenes for practical applications. Thus, our systematic analysis of the mechano-elastic and electronic properties of 2D hexagonal MBenes and their correlations advance our understandings of emergent 2D family.

Ultralow lattice thermal conductivity in type-I Dirac MBene TiB2

“…We have shown in our previous work [18], that AlB 2 -type 2D MBenes crystallizes in hexagonal P6mm 2D space group. In another work [17], we have extensively detailed the 2D crystal structure of ML and BL TiB 2 nanosheets alongwith the lattice parameters and wyckoff positions.…”

“…Many efforts are consistent towards the experimental synthesis of quasi-2D TiB 2 nanosheets using ultrasonication based liquid-phase exfoliation techniques [16,53], but to our best knowledge, no experimental data of reduction into ML or BL dimensions has been reported. In our previous works [16][17][18], we have extensively studied the ML and BL TiB 2 nanosheets for their electronic-elastic correlations and optical properties, while finding that the addition of an extra layer destroys the auxetic behavior of ML [17]. In figure 2, we present the electronic structure of ML (panels (a) and (c)) and BL (panels (b) and (d)) TiB 2 MBene.…”

“…in the form of MXenes [13,14], to the youngest addition of transition metal borides as MBenes [15][16][17][18]. Novel 2D materials MXenes are being explored for their transport dynamics [19,20].…”

“…The emerging family of 2D transitionmetal borides (MBenes) as the boron derivative of MXenes have been significantly studied for their superior catalytic activity and usage as electrode material in battery applications [21][22][23][24], which underpins the implications of charge transport in MBenes. 2D AlB 2 -type MBenes hosts a variety of intriguing electronic features including the Dirac states for TiB 2 , FeB 2 , ZrB 2 , and HfB 2 [18,[25][26][27][28], which makes them desirable for exploration of their transport dynamics. Further, to our knowledge, there are none to very few works exploring the transport dynamics of such MLs [29], however, no work has investigated the layer dependent lattice thermal conductivity and transport behavior of any Dirac MBene.…”

Hydrogenation driven ultra-low lattice thermal conductivity in β 12 borophene

“…Reducing the carbonic footprint, the scientific interest is increased in two-dimensional (2D) materials hosting intriguing properties and features beyond graphene [1], featuring many families including transition metal dichalogenides [2], transition metal carbides and carbonitrides under the family of MXenes [3,4], emerging Xene-based 2D members [5][6][7][8][9], to the youngest member in family of transition metal borides as MBenes [10][11][12]. Attributed to the quantum effects, such distinct 2D materials shows intriguing properties like high near-IR absorption, high surface area, nano-thin width, indirect to direct transitions and fascinating science [13,14].…”