Abstract
In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.
Highlights
It is an obvious fact that the atomic constituents of matter, their interactions and their spatial arrangements determine the properties of the material
While both simulations represent the main features of the measured total radial distribution functions (RDFs) reasonably well, the H–H partial radial distribution functions (pRDFs) is much better represented in the 2.44/0.46 simulation than in the 10/2 simulation
We focused mainly on the nearest neighbors to nitrogens, in order to investigate the two experimental results mentioned above; namely, the fact that nitrogen becomes tetrahedrally coordinated at low concentrations and the fact that there is an experimental upper limit to the nitrogen concentration in an amorphous carbon matrix
Summary
During the 1980s much progress was made in the experimental study of amorphous metallic multicomponent alloys—ternary, quaternary, etc. Mattern et al performed an experimental study which involved XRD and neutron scattering for three different compositions: Cu100−xZrx (x = 35, 50, 65) [30]. They found an average coordination number of 13.2, but they did not assert any particular short-range order structure present in their samples. By comparing AIMD with XRD results, and RMC with EXAFS, they obtained the 3D structures of the samples so the short range ordering could be established. Jakse and Pasturel reported an AIMD study of the g-Cu64Zr36 alloy [31,32] They obtained a coordination number closer to the one found by Mattern and co-workers, i.e., 13.1. At the end of this thermal process some stresses emerged within the samples, we geometry optimized them to relax the structures so that they could reach a local energy minimum
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
