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Materials Data on Cu3Au by Materials Project
Cu3Au is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Au is bonded to twelve equivalent Cu atoms to form AuCu12 cuboctahedra that share corners with twelve equivalent AuCu12 cuboctahedra, edges with twenty-four equivalent CuCu8Au4 cuboctahedra, faces with six equivalent AuCu12 cuboctahedra, and faces with twelve equivalent CuCu8Au4 cuboctahedra. All Au–Cu bond lengths are 2.67 Å. Cu is bonded to four equivalent Au and eight equivalent Cu atoms to form distorted CuCu8Au4 cuboctahedra that share corners with twelve equivalent CuCu8Au4 cuboctahedra, edges with eight equivalent AuCu12 cuboctahedra, edges with sixteen equivalent CuCu8Au4 cuboctahedra, faces with four equivalent AuCu12 cuboctahedra, and faces with fourteen equivalent CuCu8Au4 cuboctahedra. All Cu–Cu bond lengths are 2.67 Å.
Tuning the surface composition of Cu3Au binary alloy
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Accurate prediction of short-range order and its effect on thermodynamic, structural, and electronic properties of disordered alloys: exemplified in archetypical Cu 3 Au
Electronic-structure methods based on density-functional theory (DFT) were used to quantify the effect of chemical short-range order (SRO) on thermodynamic, structural, and electronic properties of archetypal face-centered-cubic (fcc) Cu3Au alloy. We showed that SRO can be tuned to alter bonding and lattice dynamics (i.e., phonons) and detail how these properties are changed with SRO. Thermodynamically favorable SRO significantly improved the phase stability of fcc Cu3Au from -0.0343 eV-atom -1 to –0.0682 eV-atom -1 . We used our DFT-based linear-response theory to predict SRO and its electronic origin, and accurately estimate the observed transition temperature, ordering instability (L1 2 ), and Warren-Cowley SRO parameters, in agreement with experiments. The accurate prediction of real-space SRO gives an edge over computationally and resource intensive approaches such as monte-carlo methods or experiments, which will enable large scale molecular dynamic simulations by providing supercells with optimized SRO. Here we also analyzed phonon dispersion and estimated the vibrational entropy change (from 9kB at 300 K to 6kB at 100 K) in fcc Cu3Au. We established from SRO analysis that exclusion of chemical interactions may lead to a skewed view of true properties in chemically complex alloys. The first-principles methods described in this work are generally applicable to any arbitrary solid-solution alloys, including multi-principal-element alloys, therefore, holds promise for designing technologically useful materials.
Atomistic mechanisms of the initial oxidation of stepped Cu 3 Au ( 100 )
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