Detailedab initioelectronic structure study of two approximants to Al-Mn based icosahedral quasicrystals

Abstract

The electronic structure of three available models of ␣-AlMnSi and of three models of a hypothetical approximant in the Al-Pd-Mn system are studied by means of the linear muffin-tin orbital method in the atomic sphere approximation. The effect of the atomic sphere approximation is investigated. The energy resolution of our best calculation is estimated to be 50-100 meV. By comparing the available models the importance of accurate atomic positions for the electronic structure is demonstrated. In the density of states of ␣-AlMnSi and the AlPdMn approximant a wide pseudogap ͑ϳ1 eV͒ is found near the Fermi energy. Total energies for various possible positions of the Si atoms in ␣-AlMnSi are compared. It is found to be favorable for the Si atoms to partially occupy three of the classes of inequivalent Al atoms. The full charge density of ␣-AlMnSi is calculated and compared with available experimental results. In contrast to the experimental results the strongest bonding is found to be between Si and Mn atoms.

Point contact tunneling spectroscopy of the density of states in Tb–Mg–Zn quasicrystals

“…The other relevant aspect could be related to the poor QC characteristics of the studied sample [18]. However, until today different arguments have been under different contexts [19,21,22].…”

Optimizing the thermoelectric efficiency of icosahedral quasicrystals and related complex alloys

“…This spiky component ͑over an energy scale of about 10 meV͒ is still awaiting for a definitive experimental confirmation, as it was originally obtained from self-consistent ab initio calculations, 34 and the very nature of its physical origin has been extensively debated in the literature. [35][36][37][38][39] Suitable values for the electronic model parameters appearing in Eq. ͑2͒ can be obtained by properly combining ab initio calculations with experimental transport data within a phenomenological approach previously described.…”

Ab-Initio Quantum Diffusion in Quasicrystals

“…phase, C(E F , t) is always positive, and the Boltzmann value is reached rapidly when t increases. But for some t values the velocity correlation function C(E F , t) is negative for Al 12 Mn and α-Al 114 Mn 24 . That means that at these times the phenomenon of backscattering occurs.…”

“…It is thus essential to take into account the chemical nature of the elements to analyze the electronic properties of approximants. It has been shown [24] that Si atoms are in substitution with some Al atoms. The main effect of Si is to shift E F in the pseudo-gap in agreement with Hume-Rothery mechanism to minimize band energy.…”

“…Zijlstra and S.K. Bose [24] gave a detailed ab initio electronic structure study of the α-phase. They show the difference between the DOS of the idealized 1/1 approximant and the experimental atomic structure [26].…”