Newly synthesized Zr 2 AlC, Zr 2 (Al 0.58 Bi 0.42 )C, Zr 2 (Al 0.2 Sn 0.8 )C, and Zr 2 (Al 0.3 Sb 0.7 )C MAX phases: A DFT based first-principles study

Abstract

The structural, elastic, and electronic properties of newly synthesized Zr 2 (Al 0.58 Bi 0.42 )C, Zr 2 (Al 0.2 Sn 0.8 )C, and Zr 2 (Al 0.3 Sb 0.7 )C MAX nanolaminates have been studied using firstprinciples density functional theory (DFT) calculations for the first time. Theoretical Vickers hardness has also been estimated for these compounds. All the calculated results are compared with experimental data and also with that of recently discovered Zr 2 AlC phase, where available. Zr 2 (Al 0.58 Bi 0.42 )C and Zr 2 (Al 0.2 Sn 0.8 )C are the two first Bi and Sn containing MAX compounds. The calculated structural parameters are found to be in good agreement with the experimental data. The single crystal elastic constants C ij and other polycrystalline elastic coefficients have been calculated and the mechanical stabilities of these compounds have been theoretically confirmed. The bulk modulus increases and the shear modulus decreases due to partial Bi/Sn/Sb substitution for Al in Zr 2 AlC. The calculated elastic moduli show that these Bi/Sn/Sb containing MAX phases are more anisotropic than Zr 2 AlC, and have a tendency towards ductility. The Vickers hardness decreases in the Bi/Sn/Sb containing compounds. Further, the electronic band structures and electronic density of states (EDOS) are calculated and the effects of different elemental substitution on these properties are investigated. The electronic band structures show metallic characteristics with contribution predominantly coming from the Zr 4d orbitals. Partial presence of Bi/Sn/Sb atoms increases the EDOS at the Fermi level to some extent. Possible implications of the theoretical results for these recently discovered MAX nanolaminates have been discussed in detail in this paper.

First hafnium-based MAX phase in the 312 family, Hf3AlC2: A first-principles study

“…The recent discovery of a magnetic MAX phase has extended the list of interesting properties of MAX family [7]. To date, a large number of MAX phase compounds have been synthesized [8][9][10][11][12][13][14][15][16][17] and their physical properties have also been studied [18][19][20][21][22][23][24][25][26][27]. Very recently, Lapauw et al has synthesized Hf 3 AlC 2 [28], which is the first member of 312 MAX phases in the Hf-Al-C system.…”

Point defect formation in M2AlC (M = Zr,Cr) MAX phases and their tendency to disorder and amorphize

“…Furthermore related quaternary compositions of the type Zr 2 (Al, A I )C where A I  = Sn, Sb, Pb or Bi have also been reported 8–11 . The latter study has suggested that partial substitutions on the A-site help to stabilize the Zr 2 AlC phase.…”

Elastic, mechanical, electronic, and defective properties of Zr–Al–C nanolaminates from first principles

“…The variation in bond length with the applied pressure has a close contact with the bonding characteristics. The 3.282 (LDA) 3.3 10 3.3174 32 14.405 (LDA) 14.6 10 14.6304 32 3.3294 10 3.334 33 14.556 10 14.600 33 3.319 34 14.604 34 3.3183 35 14.6178 35 3.327 36 The available experimental data on Hf-Al-C and Ti-Al-C system are listed for comparison.…”

“…49 There exist five independent elastic constants for hexagonal structures, c 11 , c 12 , c 13 , c 33 , c 44 and one dependent constant c 66 = (c 11 Àc 12 )/2. The calculated elastic constants, together with the available experimental and theoretical results from others, 6,34,37,41,42 are listed in Table 3. It can be seen that our calculated values are in good agreement with those from the previous studies.…”