Structural study of an amorphous NiZr2 alloy by anomalous wide angle X-ray scattering and Reverse Monte Carlo simulations

TL;DR

This study combines anomalous wide-angle X-ray scattering and reverse Monte Carlo simulations to elucidate the atomic structure of amorphous NiZr2 alloy, revealing distorted polyhedral units and chemical short-range order similar to a solid solution.

Contribution

It introduces a comprehensive approach integrating AWAXS, DAS, and RMC to analyze the atomic structure of amorphous alloys, providing detailed structural insights.

Findings

Identification of distorted polyhedral units in NiZr2

Good agreement between two methods for partial structure factors

Chemical short-range order similar to a solid solution

Abstract

The local atomic structure of an amorphous NiZr2 alloy was investigated using the anomalous wide-angle x-ray scattering (AWAXS), differential anomalous scattering (DAS) and reverse Monte Carlo (RMC) simulations techniques. The AWAXS measurements were performed at eight different incident photon energies, including some close to the Ni and Zr K edges. From the measurements eight total structure factor S(K,E) were derived. Using the AWAXS data four differential structure factors DSFi(K,Em,En) were derived, two about the Ni and Zr edges. The partial structure factors SNi-Ni(K), SNi-Zr(K) and SZr-Zr(K) were estimated by using two different methods. First, the S(K,E) and DSFi(K,Em,En) factors were combined and used in a matrix inversion process. Second, three S(K,E) factors were used as input data in the RMC technique. The coordination numbers and interatomic distances for the first neighbors extracted from the partial structure factors obtained by these two methods show a good agreement. By using the three-dimensional structure derived from the RMC simulations, the bond-angle distributions were calculated and they suggest the presence of distorted triangular-faced polyhedral units in the amorphous NiZr2 structure. We have used the Warren chemical short-range order parameter to evaluate the chemical short-range order for the amorphous NiZr2 alloy and for the NiZr2 compound. The calculated values show that the chemical short-range order found in these two materials is similar to that found in a solid solution.