Ab initio electronic structure, bonding and optical properties of two relatively new ceramics Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 : A comparative study
| Autor: | Muhammad Azhar Khan, Muhammad Rafiq, Faisal Iqbal, Salman Mehmood, M. Nasir Rasul, Altaf Hussain, Rohail Ali Shah |
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| Rok vydání: | 2018 |
| Předmět: |
Materials science
Fermi level Analytical chemistry General Physics and Astronomy 02 engineering and technology Electronic structure 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Optical conductivity Bond order Effective nuclear charge 0104 chemical sciences symbols.namesake Delocalized electron Linear combination of atomic orbitals symbols 0210 nano-technology Electronic band structure |
| Zdroj: | Chinese Journal of Physics. 56:30-39 |
| ISSN: | 0577-9073 |
| DOI: | 10.1016/j.cjph.2017.12.001 |
| Popis: | The structural, electronic and optical properties of the ternary carbides Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 are studied via first principles orthogonalized linear combination of atomic orbitals (OLCAO) method. Results on crystal structure, interatomic bonding, band structure, total and partial density of states (DOS), localization index (LI), effective charge ( Q *), bond order (BO), dielectric function (e), optical conductivity (σ) and electron energy loss function are presented and discussed in detail. The band structure plots show the conducting nature of Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 carbides. DOS results disclose that the total number of states at Fermi level N( E F ) are 1.89 and 2.38 states/(eV unit cell) for Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 respectively. The Q * calculations show an average charge transfer of 0.723 and 0.711 electrons from Hf and 0.809 and 0.807 electrons from Al to C sites in Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 respectively. The BO results provide the dominating role of Al–C bonds with BO value of 6.62 (BO% = 59%) and 6.66 (BO% = 49%) for Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 respectively and are considered responsible for the crystals cohesion. The LI results reflect the presence of highly delocalized states in the vicinity of the Fermi level. The dielectric function plots of the real (ɛ 1 (ℏω)) and imaginary (ɛ 2 (ℏω)) parts show the anisotropic behavior of Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 . The results on optical conductivity (σ) support the trends observed in dielectric functions. The electron energy loss functions reveal the presence of sharp peaks both in ab-plane and along c -axis around 20 eV in Hf 2 Al 3 C 4 and Hf 3 Al 3 C 5 ternary carbides. |
| Databáze: | OpenAIRE |
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