New Approaches to the Computer Simulation of Amorphous Alloys: A Review

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.

Short-range order in ab initio computer generated amorphous and liquid Cu–Zr alloys: A new approach

“…On the other hand, a larger time step (3DTS) lets the dynamics of the system evolve better within the undermelt-quench framework without atomic overlaps, atomic collisions or without compromising the SCF convergence. Therefore this strengthens the fact, as previously proven [44,45], that 3DTS is the best time step to generate an amorphous structure with the undermeltquench method. Then we consider that 3DTS samples are more representative and these are the ones that we shall compare with experiment.…”

On Structure and Properties of Amorphous Materials

“…Reviews of the methods have been published by Drabold [103], and in this issue by Valladares et al [104]. In view of this, only a few selected papers will be mentioned with specific interests to the present review.…”

Influence of spatial and temporal coherences on atomic resolution high angle annular dark field imaging

“…Finally, the supercell of desired rectangular geometry was cut from generated IAS sphere. More realistic models for amorphous layers require very complicated and time-consumable calculations in frames of Molecular Dynamic (MD) simulations [35]. Furthermore, the resulting structure is extremely sensitive to the initial conditions such as the initial temperature and the quenching rate.…”