Structural and Electronic Properties of Cu 64 Zr 36 BMG by ab initio Molecular Dynamics
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Structural and Electronic Properties of Cu64Zr36 BMG by ab initio Molecular Dynamics Jonathan Galván-Colín1, Ariel A. Valladares1, Alexander Valladares2, Renela M. Valladares2 1 Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D. F. 04510, México 2 Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-542, México, D. F. 04510, México
ABSTRACT Much attention has been given to bulk metallic glasses (BMG) in recent years, particularly those based on binary alloys due to the simplicity of their atomic composition. Although efforts to understand the atomistic features that give rise to their exceptional properties have been made, the electronic and vibrational properties have been disregarded. We undertook the task of simulating the Cu64Zr36 glassy metal using a supercell with 108 atoms and a different simulational approach: the undermelt-quench approach [1]. The structure was characterized by means of the radial (pair) distribution function and the bond-angle distribution and the electronic density of states was calculated. We find that our results agree well with experimental data.
INTRODUCTION Although the research on glassy metals increased in the late 1980s it was primarily focused on multicomponent amorphous alloys: binary, ternary, etc., mainly due to the fact that the presence of several atomic species in an alloy improved the disorder in the structure, thus avoiding recrystallization. However, from a computational point of view binary metallic alloys were considered the best alloys to study because their simple composition would simplify the study of the atomic phenomena that give rise to the disordered structure. Particularly, Cu-Zr alloys have gained a lot of attention for they have proven to be good glassy samples formers [2– 6]. Experimental works concerning the characterization of Cu-Zr alloys—particularly the Cu64Zr36 concentration—have been reported [6, 7]. Furthermore, this system has also been studied from the DFT-based simulational point of view where a common approach is used: melting the sample with a subsequent fast quenching stage below the undercooled region to avoid crystallization [8, 9]. In the present work we applied a variant of a previously used ab initio approach which has been demonstrated to lead to good results for semiconducting amorphous structures [10–12] and metallic structures such as amorphous and liquid aluminum [1, 13]: the undermelt-quench approach. We report the corresponding total and partial radial (pair) distribution functions (PDFs) in order to study the atomic arrangement in each supercell. We carried out a bond-angle distribution (BAD) [14] analysis for exhibiting if icosahedral ordering was present in our samples. We pondered over agreements and disparities with experimental data and other ab initio simulations results.
METHOD To simulate the Cu64Zr36 amorphous alloy we employed the simulated annealing task implemented on DMol3 [15], a DFT-based code included in the Materi
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