EXAFS measurements and reverse Monte Carlo modeling of atomic structure in amorphous Ni80P20 alloys

• Published in: Journal of non-crystalline solids Vol. 354; no. 10-11; pp. 945 - 955
• Main Authors: LUO, W. K, MA, E
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.02.2008
• Subjects: ALLOY SYSTEMS; ALLOYS; Amorphous semiconductors, metals, and alloys; ATOMS; Condensed matter: structure, mechanical and thermal properties; Disordered solids; Exact sciences and technology; MATERIALS SCIENCE; MIXING HEAT; MONTE CARLO METHOD; national synchrotron light source; Physics; PROCESSING; RESOLUTION; SIMULATION; SOLUTES; Structure of solids and liquids; crystallography; X-RAY SPECTROSCOPY; Polyamorphism; Reverse Monte Carlo method; Nickel alloys; 61.10.Ht; 61.43.Dq; 61.25.Mv; 61.20.Ja; metallic glasses; Synchrotron radiation; Monte Carlo simulations; Medium-range order; Short-range order; Medium range order; Amorphous alloy; Amorphous metals; Phosphorus alloys; EXAFS; Local structure; Atomic arrangement; Short-range order; Modelling; Atomic structure; Amorphous state structure; Synchrotron radiation
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2007.08.028

This paper presents a full account of the EXAFS measurements and reverse Monte Carlo (RMC) modeling of the atomic arrangements and short-to-medium range structure in an amorphous Ni-P alloy, expanding on the description included in our recent publication. The atomic packing is analyzed from the standpoint of solute atoms. The short-to-medium range structure is discussed based on single-solute-centered quasi-equivalent clusters that form due to strong chemical short-range ordering, and the topological order is described in terms of both intra-cluster and inter-cluster dense packing for efficient filling of space. This analysis is also conducted for amorphous Ni80P20 prepared via different processing routes, to observe if the polyamorphism suggested in literature for amorphous Ni-P can be confirmed from the local structure perspective. The structural differences between the proposed polymorphs are apparently subtle and a full resolution of this issue is found to be beyond the capabilities of our EXAFS/RMC modeling approach. The amorphous structural features uncovered are also compared briefly with those observed before in amorphous alloy systems with positive heat of mixing.