A Novel Theoretical Study of Elastic and Electronic Properties of M₂CdC (M = Zr, Hf, and Ta) MAX Phases

Abstract

In this study, we have investigated the structural, electronic, and elastic properties of the M2CdC (M = Ta, Zr, and Hf) MAX phases, using the first-principle methods based on the density functional theory. The calculated formation energies revealed that these compounds are thermodynamically stable in the hexagonal MAX phase. The stability is confirmed by the elastic constants and the conditions of mechanical stability criterion. Also, we have determined the bulk and shear modules of the Young modulus and the Poisson coefficient. The band structures indicate that the three materials are electrically conductive. The chemical bond in M2CdC is covalent-ionic in nature with the presence of metallic character. For the density of states the hybridization peak between M d and C p occurs in the lower energy range. We have found that there is no gap for these materials due to the existence of a maximum peak of DOS around Fermi level.

DFT insights into Nb-based 211 MAX phase carbides: Nb2AC (A = Ga, Ge, Tl, Zn, P, In, and Cd)

“…65 They are machinable, just like metals, as stated in the preceding section, and brittle, just like ceramic materials. But, some of them are also ductile, 53,55,66 making them more machinable and, consequently, more useful owing to easy shaping. By using the Pugh ratio (G/B) 67 and Poisson's ratio (y), 68 the ductile/brittle characteristics of Nb 2 AC (A = Ga, Ge, Tl, Zn, P, In, Cd, and Al) have been evaluated and are presented in Table 2.…”

A novel theoretical study of elastic and electronic properties of Os2YAl, (Y=Sc, Ti, V) Heusler Alloys

“…To confirm the structural stability we calculated the cohesion energy and the energies of the individual atoms by increasing the unit cell of a face-centered cubic structure [39] up to 30 Bohr (about 16 Å) for the three compounds. The cohesion energy E Os 2 yAl coh of Os 2 YAl (Y=Si, Ti, V) is known as the overall energy of the constituent atoms minus the total energy of the compound is given by [39,40]…”

First-principles study of the structural, electronic, and elastic properties of Sc2SiX (X=C, N)

“…To see the relative phase stabilities, we calculated the energy of formation for Sc 2 Si X,X=(C,N) using [5,25]…”

“…To confirm the structural stability we have calculated the cohesive energy of each compound using Eq. (2) [5,25,30]. Coh , E Si Coh , E C Coh , E N Coh are the isolated atomic energies of the pure constituents [25].…”

“…Despite their relatively old discovery, their physical properties have been relatively little studied and it was not until 1996 that a systematic work of synthesis and characterization was undertaken by an American team from Drexel University (Philadelphia) led by Mr. Barsoum [4]. Most of the MAX phases are of M 2 AX stoichiometry with the space group P63 / mmc [5]. Figure 1 shows the crystal structure of Sc 2 SiX.…”