Electronic distributions of Al-Mn and Al-Mn-Si alloys

Abstract

Electronic distributions of various symmetries have been investigated for both valence and conduction bands in a series of Al-Mn and Al-Mn-Si alloys of different structural states (amorphous, quasi-crystalline or crystalline) and Mn concentrations ranging from 14 to 22 at.%. Experiments have been carried out by means of soft-X-ray emission and photoabsorption spectroscopies. This allowed the authors to provide a complete description of the valence band states and to confirm the progressive opening of a small gap in the Al-sp DOS at the Fermi level with increasing Mn concentration in the alloys. At a given Mn concentration the gap is wider for the quasi-crystalline phase than for its crystalline counterpart.

Interplay between electronic structure and medium-range atomic order in hexagonalβ−Al9Mn3SiLaissardière1 2003Phys. Rev. B10090View full textAdd to dashboardCite

“…Local DOS's of ␤ are also shown free states is clearly seen. A large d band, from Ϫ2 to 2 eV, is due to a strong sp-d hybridization in agreement with experimental results [45][46][47][48][49] and with ab initio calculations 15,50-52 for Al-TM crystals and quasicrystals.…”

Covalent Bonds in AlMnSi Icosahedral Quasicrystalline Approximant

“…This binding peak is mainly due to the local projected DOS of the Mn d state, the Al p state of the first shell, and the second shell of MI cluster, which together are responsible for the stability of the MI cluster. As mentioned previously, SXES measurements by Belin et al showed that hybridization between the Al p band and Mn d band is responsible for the opening in the pseudogap near E F [15]. Our real-space image of electron density distributions enables the strong covalent Mn-Al bond in a-AlMnSi to be described using their band structure calculation and X-ray spectroscopic measurements.…”

“…Kimura et al surmised that metallic-covalent bonding conversion in icosahedral clusters of aluminum or boron is closely related to the metal-nonmetal transition in both Al-based icosahedral quasicrystals/approximants and B-based approximants [13,14]. In addition, results of photoemission spectroscopy and soft-x-ray emission spectroscopy (SXES) suggest that strong p-d hybridization between Al-TM atoms plays a crucial role in enhancing nonmetallic properties [15,16].Therefore, the x-ray charge density study should be required to reveal a bonding nature in order to give a better understanding for the electronic structure of a quasicrystal approximant.In this Letter, we use the maximum entropy method (MEM) with synchrotron radiation powder data to examine the bonding nature of icosahedral clusters of 12 atoms in nonmetallic a-AlMnSi 1͞1-cubic approximant phase and 13 atoms in metallic Al 12 Re phase, respectively.Briefly, ingots of Al 12 Re and Al 72 Mn 16 Si 12 alloys were prepared from elemental constituents (3N) by arc melting under Ar atmosphere. To obtain single-phase bulk samples of Al 12 Re crystal phase, Al-Re alloy ingots were placed in an evacuated quartz tube and heated to 1023 K, which is slightly below the peritectic point, and held for 5 h. The samples were then cooled to 975 K over 16 h. Sample homogenization of Al-Mn-Si alloy ingots was achieved by remelting via inductive melting, after which single-phase bulk samples of a-AlMnSi crystal phase were prepared by annealing the ingots at 953 K for 17 h under Ar atmosphere.…”

“…Kimura et al surmised that metallic-covalent bonding conversion in icosahedral clusters of aluminum or boron is closely related to the metal-nonmetal transition in both Al-based icosahedral quasicrystals/approximants and B-based approximants [13,14]. In addition, results of photoemission spectroscopy and soft-x-ray emission spectroscopy (SXES) suggest that strong p-d hybridization between Al-TM atoms plays a crucial role in enhancing nonmetallic properties [15,16].…”

Covalency, semiconductor-like and thermoelectric properties of Al-based quasicrystals: icosahedral cluster solids

“…This result experimentally supports the idea of metallic-covalent bonding conversion in the icosahedral cluster, as revealed by the molecular orbital calculation. Soft X-ray emission spectroscopic studies by Belin et al [16] and Takeuchi et al [17] showed that hybridization between the Al p band and the Mn d or Re d band is responsible for the opening in the pseudogap near E F . In this work, we have observed the real-space image of the strong Mn±Al covalent bonds in a-AlMnSi which were discussed in such spectroscopic study.…”