The electronic and magnetic structure of Fe-based bulk amorphous metals: An ab-initio approach
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The electronic and magnetic structure of Fe-based bulk amorphous metals: An ab-initio approach Yang Wang1, Mike Widom2, Don Nicholson3, Marek Mihalkovic2, and Siddartha Naidu2 1 Pittsburgh Supercomputing Center, Carnegie Mellon University, Pittsburgh, PA 15213 2 Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 3 Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 ABSTRACT We applied the locally self-consistent multiple scattering (LSMS) method to the study Fe-based bulk amorphous metals. The LSMS method is an order-N approach to the electronic structure calculation for solid state materials based on density functional theory and local density approximation. Using LSMS method, we performed electronic structure calculations for the supercell samples generated by ab-initio molecular dynamics simulation. The equilibrium atomic volume and the bulk modulus are calculated based on the energy versus volume curve. The magnetic moment distribution in the samples is determined for both collinear and noncollinear cases. A comparison with the experimental results is also made.
INTODUCTION Amorphous metals prepared by rapid quenching technique from the liquid state were first reported in 1960 [1]. Also known as metallic glasses, they differ from ordinary metals in that their constituent atoms are not arranged on a crystalline lattice. Because of this, they exhibit unique combination of physical properties and have attracted much attention from both industrial and academic institutions [2,3]. Nevertheless, until recently, they have largely been manufactured in the form of thin ribbons usually less than 1mm in thickness, because fast cooling rates (~ 106 ˚K/sec) are required for retaining the metastable amorphous phase. And as a result, they have not attained an important role of industrial applicability. The first reported bulk amorphous metals were Pd-based alloys developed in the early 1980s [4,5]. Of these, Pd-Ni-P alloys were prepared with thicknesses up to 1 cm [5] which demonstrated that the 1mm thickness limits can be surmounted. But they did not draw sufficient interests from industry due to the high cost of palladium. The real breakthrough came during the period from 1988 to 1990 when Inoue et al. [6-8] discovered multicomponent liquid alloys with very deep eutectics capable of freezing to a glassy state of several cm thick by conventional cooling methods. This indeed proved to be a turning point in opening up a new field of research. Beginning with Mg- [6], Ln- [7] and Zr- [8] based quaternary alloys, Inoue extended bulk amorphous metal formation to Fe-, Ni- and other alloy families. (See reference [9] for a historical summary on Inoue’s discovery of bulk amorphous metals.) Johnson’s group developed Zr-Ti-based and other sizable amorphous metals [10-12]. Poon et al. proposed Zr-B and Mo-C backbone structure model in Fe-based bulk amorphous metals, and recently produced Fe-Mnbased bulk glass samples [13]. Bulk amorphous metals exhibit low volume s
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