Structural, electronic and elastic properties of Ti2TlC, Zr2TlC and Hf2TlC

Abstract

Abstract:Using First-principle calculations, we have studied the structural, electronic and elastic properties of M 2 TlC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell is in good agreement with the available experimental data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the -axis than along the axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure. The band structures show that all three materials are electrical conductors. The analysis of the site and momentum projected densities shows that bonding is due to M -C and M -Tl hybridizations. The M -C bonds are lower in energy and stiffer than M -Tl bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus and Poisson's ratio for ideal polycrystalline M 2 TlC aggregates. We estimated the Debye temperature of M 2 TlC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Ti 2 TlC, Zr 2 TlC, and Hf 2 TlC compounds that requires experimental confirmation. 61.66.; 62.20.de; 71.15.Mb; 71.20 PACS (2008): .Gj Keywords:MAX phases • structural properties • electronic properties • elastic properties • pressure effect © Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Ab initio study of the structure, elastic, and electronic properties of Ti3(Al1−nSin)C2 layered ternary compounds

“…Withthe characteristics of metallic as well as ceramics materials 15 , where each group member contains at least two forms of ionic, covalent, or metallic chemical bonds 16 . The MAX phases such as Ti 3 SiC 2 and Ti 3 AlC 2 are a 312 class of layered ternaries where the individual phases differ by the number of M-layers parting the A-layers in the 312-MAX phases 17 – 21 . These compounds combine some characteristics of metals like strong compressive strength, high fracturing strength, hardness, ductility, good electrical and thermal conductivity, high stiffness, damage tolerance, relatively low thermal expansion coefficient.…”

“…First-principles approaches are widely employed to study the properties of MAX phases, for example, M 2 GaN (M = Ti, V and Cr) 27 , Ti 2 TlC, Zr 2 TlC, and Hf 2 TlC 17 , 23 , Ti 3 AlC 2 and Ti 2 SiC 2 20 . Zhou et al 28 reported the distribution of charge density on the (1120) plane of Ti 3 AlC 2 , where robust directional Ti-C-Ti-C-Ti covalent bond chains were observed that linked to fairly weaker Ti–Al covalent bindings.…”

Ab initio Study of the Structure, Elastic, and Electronic Properties of Ti3(Al1-nSin)C2 Layered Ternary Compounds

“…Specific forms of MAX phases called 211, 312, or 413 (and higher orders such as 514, 615, and 716) are known in the literature. These numbers denote the stoichiometry of MAX phase materials, for example, Ti2SiC and Ti2AlC represent 211 MAX phases, Ti3SiC2 and Ti3AlC2 denote 312-MAX phase while 413-type are the Ti4SiC3 and Ti4AlC3, indicating that the individual phases differ by the number of M layers parting the A-layers, that is there are two in the 211-type, three in the 312-type, and four M-layers in the 413 MAX phase-type [1][2][3]8 .…”

“…MAX phases are useful in numerous applications due to their unique, hybrid ceramic/metal properties, that result from their structure as well as their atomic arrangements 1,8,9 . More categorically, these materials are considered for purposes in extreme environments as they exhibit outstanding oxidation resistance and thermal stability.…”

“…First-principles approaches are widely employed to study MAX phases, for example, M2GaN (M=Ti, V and Cr) 15 , Ti2TlC, Zr2TlC and Hf2TlC 8,11 , Ti3AlC2 and Ti2SiC2 3 . Zhou et al 16 reported the distribution of charge density on the (1120) plane of Ti3AlC2, where robust directional Ti-C-Ti-C-Ti covalent bond chains were observed that linked to fairly weaker Ti-Al covalent bindings.…”