Structure, energetics, and bonding of amorphous Au–Si alloys

Abstract

First principles periodic calculations based on gradient-corrected density functional theory have been performed to examine the structure, energetics, and bonding of amorphous Au-Si alloys with varying Au:Si composition ratios. Our results predict that the Au-Si alloy forms the most stable structure when the Si content is around 40-50 at. %, with an energy gain of about 0.15 eV/atom. In addition, the volume change per atom in the alloy exhibits a distinctive nonlinear trend, with the minimum value around 60 at. % Si. The occurrence of the minimum in the Au-Si mixing energy and volume is attributed to strong hybridization of the Au 5d-Si 3p states. We also present variations in the radial distribution function and atomic coordination number as a function of Au:Si composition ratio, with discussion of the nature of local packing and chemical bonding in the Au-Si alloy system.

Theoretical search for possible Au-Si crystal structures using a genetic algorithm

“…1), in which, the most stable structures are also Au-rich. In our prediction, the most stable one is of composition 50.0% of Au content, this also agrees with the results from literature, 13 which suggested that the stable Au-Si alloy should be around Au content 50.0% to 60.0%.…”

“…simulations, 26 and revealed that Au and Si atoms are very reactive with each other, 13,27 and lead to strong intermixing between Si and Au atoms. 26 By first-principles electronic structure calculations, Tasci et al predicted a new ground-state of crystalline Au 4 Si in spite of no Au-Si compounds have been shown in the existing phase diagram.…”

“…Although the Au-Si amorphous alloy exhibits remarkable physical properties, the atomic structure and formation mechanism of amorphous alloys remain poorly understood. 10,13,14 Gold silicide structures at different compositions have also been an interesting subject of research and have attached a lot of investigations. Various experimental methods have been used such as evaporation, irradiation, [15][16] sputter deposition, blast-atomizing rapid quenching and X-ray-diffraction (XRD) to investigate the formation and structures of possible stable and metastable phases of gold silicide.…”

“…28 Lee et al examined the atomic structures, energetics, and the bonding of amorphous Au-Si alloys. 13 They also studied the surface segregation behavior of Si in amorphous Au-Si alloys using AIMD. 27 Lee's results predicted that stable structure of Au-Si alloys can be formed when the Si content is around 40-50%, with an energy gain about 0.15 eV/atom.…”

Structural Features of the Extraordinary Low Glass Transition Temperature for Au₆₅Cu₁₈Si₁₇ Bulk Metallic Glass

“…16) Theoretical calculations based on the first principle, however, indicate strong hybridization between Au 5d and Si 3p states. 17) It is also suggested that there is a clustering of Au around Si atoms for Au-rich system such that the Si atoms are uniformly distributed.…”