Theoretical prediction, synthesis, and crystal structure determination of new MAX phase compound V2SnC

Abstract

Guided by the theoretical prediction, a new MAX phase V 2 SnC was synthesized experimentally for the first time by reaction of V, Sn, and C mixtures at 1000 ℃. The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and high resolution scanning transmission electron microscopy (HR-STEM). The stacking sequence of V 2 C and Sn layers results in a crystal structure of space group P6 3 /mmc. The a-and c-lattice parameters, which were determined by the Rietveld analysis of powder XRD pattern, are 0.2981(0) nm and 1.3470(6) nm, respectively. The atomic positions are V at 4f (1/3, 2/3, 0.0776(5)), Sn at 2d (2/3, 1/3, 1/4), and C at 2a (0, 0, 0). A new set of XRD data of V 2 SnC was also obtained. Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy, satisfied Born-Huang criteria of mechanical stability, and positive phonon branches over the Brillouin zone. It also has low shear deformation resistance c 44 (second-order elastic constant, c ij) and shear modulus (G), positive Cauchy pressure, and low Pugh's ratio (G/B = 0.500 < 0.571), which is regarded as a quasi-ductile MAX phase. The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.

Electrochemical Lithium Storage Performance of Molten Salt Derived V2SnC MAX Phase

“…In 2020, a new V 2 SnC MAX phase was first reported by Xu et al [ 19 ] via solid phase reaction of V, Sn, and C mixtures. Thus, further investigation on synthesizing this new V 2 SnC MAX phase in a facile way and exploring its potential application as electrode materials for Li-ion batteries is with great significance.…”

Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering

“…Even though the crystal structure of Y 3 Si 2 C 2 is different than hexagonal structure (space group P6 3 /mmc) of typical MAX phases (where M is an early transition metal, A is an A-group element, and X is carbon or nitrogen [4]), both phases have similar characteristics of layered structure and anisotropic bonding. Therefore, they both exhibit anisotropic electrical conductivity, anisotropic mechanical properties, and a low shear deformation resistance [3,[5][6][7]. Zhou et al [3] theoretically predicted that the bulk modulus and shear modulus of Y 3 Si 2 C 2 are 93 and 50 GPa, respectively.…”

DFT insights into the electronic structure, mechanical behaviour, lattice dynamics and defect processes in the first Sc-based MAX phase Sc2SnC

“…The Sc atoms occupy the 4f Wyckoff site with the fractional coordinates (1/3, 2/3, z), the Sn resides in the 2d atomic site with the fractional coordinates (1/3, 2/3, 3/4) and the C atoms take position at the 2a Wyckoff position with the fractional coordinates (0, 0, 0). The optimized lattice parameters are listed in Table S1 in the supplementary section along with those of all M2SnC MAX phases including experimental values 8,10,[30][31][32] . The present values for Sc2SnC show very good agreement with the experimental values, suggesting the validity of the present investigation.…”