Electronic structure of random Ag sub 0. 5 Pd sub 0. 5 and Ag sub 0. 5 Au sub 0. 5 alloys
- Solar Energy Research Institute, Golden, Colorado 80401 (United States)
The electronic density of states and mixing enthalpies of random substitutional {ital A}{sub 1{minus}{ital x}B{ital x}} alloys have often been described within the single-site coherent-potential approximation (SCPA). There one assumes that each atom interacts with a fictitious, highly symmetric average medium and that at a given composition {ital x}, all {ital A} atoms (and separately, all {ital B} atoms) are equivalent (i.e., have the same charges and atomic sizes). In reality, however, a random alloy manifests a distribution of different (generally, low-symmetry) local environments, whereby an atom surrounded locally mostly by like atoms can have different charge-transfer or structural relaxations than an atom surrounded mostly by unlike atoms. Such environmental effects'' (averaged out in the SCPA) were previously studied in terms of simple model Hamiltonians. We offer here an efficient method capable of describing such effects within first-principles self-consistent electronic-structure theory. This is accomplished through the use of the special-quasirandom-structures'' (SQS) concept (Zunger {ital et} {ital al}., Phys. Rev. Lett. 65, 353 (1990)), whereby the lattice sites of a periodic supercell'' are occupied by {ital A}'s and {ital B}'s in such a way that the structural correlation functions closely mimic those of a perfectly random infinite alloy. The self-consistent charge density, total and local density of states, and mixing enthalpies are then obtained by applying band theory (here, the linearized augmented-plane-wave method) to the SQS. Application to Ag{sub 0.5}Pd{sub 0.5} and Ag{sub 0.5}Au{sub 0.5} alloys clearly reveals environmental effects; that is, the charge distribution and local density of states of a given atomic site depend sensitively not only on the composition and occupation of the site but also on the distribution of atoms around it.
- DOE Contract Number:
- AC02-77CH00178
- OSTI ID:
- 6119878
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 44:19; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GOLD
ELECTRONIC STRUCTURE
PALLADIUM ALLOYS
SILVER ALLOYS
BINARY ALLOY SYSTEMS
ELECTRON DENSITY
MIXING HEAT
RANDOMNESS
SELF-CONSISTENT FIELD
ALLOY SYSTEMS
ALLOYS
ELEMENTS
ENTHALPY
METALS
PHYSICAL PROPERTIES
PLATINUM METAL ALLOYS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
360104* - Metals & Alloys- Physical Properties