Electronic structure of ordered and disordered Cu sub 3 Au and Cu sub 3 Pd

Journal Article · Fri May 01 00:00:00 EDT 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.10314· OSTI ID:7294854

Lu, Z W; Wei, S; Zunger, A ^[1]

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1. National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

In ordered {ital L}1{sub 2}-type {ital A}{sub 3}{ital B} compounds, each {ital A} atom is coordinated by 8{ital A}+4{ital B} atoms, while each {ital B} atom is coordinated by 12{ital A} atoms. By symmetry, all {ital A}-{ital A}, {ital A}-{ital B}, and {ital B}-{ital B} bond lengths are equal. When this structure disorders to form the substitutionally random {ital A}{sub 0.75}{ital B0.25} alloy, each atom acquires a {ital distribution} of different types of coordination shells. Concomitantly with this reduction in site symmetries, (i) topologically different {ital A} atoms (and separately, different {ital B} atoms) can have unequal charges, and (ii) the various bonds need not be of equal average lengths {l angle}{ital R}{r angle} (i.e., {l angle}{ital R}{sub {ital A}-{ital A}}{r angle}{ne}{l angle}{ital R}{sub {ital A}-{ital B}}{r angle}{ne} {l angle}{ital R}{sub {ital B}-{ital B}}{r angle}). Furthermore, (iii) there can be a distribution of bond-length values around {l angle}{ital R}{sub {ital i}{ital j}}{r angle} for each of the three chemical bond types. In this work we study the effects of such charge fluctuations (i) and relaxational fluctuations ((ii) and (iii)) on the electronic structure of Cu{sub 3}Au and Cu{sub 3}Pd. The random alloys are modeled by the special quasirandom structure (SQS), whereby the sites of a periodic supercell are occupied by {ital A} and {ital B} atoms so that the first few radial correlation functions closely reproduce the average correlation functions in an infinite substitutional random network. Instead of requiring that each atom see'' an identical, average medium, as is the case in the homogeneous site-coherent-potential approximation (SCPA), we thus create a distribution of distinct local environments whose average corresponds to the random alloy.

• DOE Contract Number: AC02-77CH00178
• OSTI ID: 7294854
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 45:18; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER BASE ALLOYS
ELECTRONIC STRUCTURE
GOLD ALLOYS
PALLADIUM ALLOYS
BINARY ALLOY SYSTEMS
CHEMICAL BONDS
ENERGY-LEVEL DENSITY
FLUCTUATIONS
FORMATION HEAT
ALLOY SYSTEMS
ALLOYS
COPPER ALLOYS
ENTHALPY
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
REACTION HEAT
THERMODYNAMIC PROPERTIES
VARIATIONS
360104* - Metals & Alloys- Physical Properties