Abstract
We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2PbC, Zr2PbC, and Hf2PbC using the first-principles calculations. These structures display nanolaminated edifices where MC layers are interleaved with Pb. The calculation of formation energies, elastic moduli and phonons reveal that all MAX phase systems are exothermic, and are intrinsically and dynamically stable at zero and under pressure. The mechanical and thermal properties are reported with fundamental insights. Results of bulk modulus and shear modulus show that the investigated compounds display a remarkable hardness. The elastic constants C11 and C33 rise more quickly with an increase in pressure than that of other elastic constants. Electronic and bonding properties are investigated through the calculation of electronic band structure, density of states, and charge densities.
Highlights
We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2 PbC, Zr2 PbC, and Hf2 PbC using the first-principles calculations
The breakthrough development that set off a renaissance came throughout the 1990s, when Barsoum and El-Raghy [2,3,4] synthesized nearly phase-pure samples of Ti3 SiC2, and uncovered a material with an extraordinary mix of ceramic and metallic properties
Our findings show that the computed C11, C33, Young’s modulus, and bulk modulus values increase remarkably when compared to other elastic constants, whereas the C66 and shear modulus change more gradually
Summary
All calculations are implemented in the Quantum Atomistix ToolKit (quantumATK) [37]. package using the density functional theory (DFT) within the local combination of the atomic orbitals (LCAO) approach. All calculations are implemented in the Quantum Atomistix ToolKit (quantumATK) [37]. Package using the density functional theory (DFT) within the local combination of the atomic orbitals (LCAO) approach. The optimized geometry structures were obtained using the limitedmemory Broyden-Fletcher-Goldfarb-Shanno minimization technique, with force on each atom site fewer than 0.05 eV/Å. A 4 × 4 × 3 MonkhorstPack [40] k-grid is used, and for electronic property calculations, a 10 × 10 × 8 grid is used. Because of the strong relativistic effect owing to the existence of heavy Pb element, spin orbital coupling (SOC) contribution is taken account of the electronic structure calculations. The phonon dispersion was computed using a dynamical matrix based on a FD method, implemented in quantum ATK [37]
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