Ab initio electronic structure, bonding and optical properties of two relatively new ceramics Hf2Al3C4 and Hf3Al3C5: A comparative study

作者：Mehmood Salman^*; Rasul M Nasir; Rafiq Muhammad Amir; Shah Rohail Ali; Khan Muhammad Azhar; Iqbal Faisal; Hussain Altaf^*

来源：Chinese Journal of Physics, 2018, 56(1): 30-39.

DOI：10.1016/j.cjph.2017.12.001

• Ternary carbides
• Electronic structure
• Optical properties
• ab initio calculations

The structural, electronic and optical properties of the ternary carbides Hf2Al3C4 and Hf3Al3C5 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 (epsilon), optical conductivity (sigma) and electron energy loss function are presented and discussed in detail. The band structure plots show the conducting nature of Hf2Al3C4 and Hf3Al3C5 carbides. DOS results disclose that the total number of states at Fermi level N(EF) are 1.89 and 2.38 states/(eV unit cell) for Hf2Al3C4 and Hf3Al3C5 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 Hf2Al3C4 and Hf3Al3C5 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 Hf2Al3C4 and Hf3Al3C5 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 (epsilon(1)(h omega)) and imaginary (epsilon(2)(h omega)) parts show the anisotropic behavior of Hf2Al3C4 and Hf3Al3C5. The results on optical conductivity (sigma) 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 Hf2Al3C4 and Hf3Al3C5 ternary carbides.

• 出版日期2018-2